Chapter 1: A Fated Meeting—The Older Woman and Younger Boy

A little over five years ago—

On a certain autumn holiday, Yurika, then a high school senior, was walking with a permanently displeased expression on her face. She was on her way to a family restaurant to meet the woman her father was planning to remarry.

"Seriously, why a remarriage all of a sudden?" Yurika muttered to no one in particular.

In the few years since her parents' divorce, Yurika had been quietly enjoying her freedom. Her father’s sudden declaration of remarriage had brought a storm into her peaceful life.

It wasn't that she had any particular attachment to her biological mother. That woman had been nothing but trouble—hardly someone worth praising—and Yurika had found life quite comfortable once she was gone. She didn't care who her father dated now that he was single again.

However, having a complete stranger move into her home was a different matter entirely.

She was already exhausted from the relationship with her real mother; the idea of a stepmother was out of the question. Her territory, where she could do as she pleased, was about to be destroyed. She could not forgive someone else encroaching upon her sanctuary—her home.

"I'm only meeting her, and that's it!" Yurika’s tone was sharp.

After her father had pleaded with her numerous times, she had reluctantly agreed to the meeting. However, she was already planning to turn the proposal down as soon as they met in person. Things were going well as they were; she didn't want to introduce unnecessary problems into the household.

"Yurika, don't make such a scary face. This is the first time both families are meeting, after all."

Seeing Yurika’s incredibly foul mood, her father, Mikiya, spoke up in an attempt to soothe her. If she stayed this prickly, the first meeting would be a complete disaster.

Akashi Mikiya.

Yurika’s biological father. He was a man of average build with a gentle expression—serious, but with an air of being somewhat clumsy. After being jerked around by his flashy, playgirl of a wife, he had been unilaterally served divorce papers and became a divorcee. Yurika’s custody had been awarded to Mikiya, who had a stable income, rather than her mother, whose lifestyle was volatile.

Yurika turned a sulky face toward Mikiya, who seemed to think everything would just work out.

"Hah? Like I care."

"Don't say that... The woman I'm seeing, Emiko-san, is kind and has a great personality. And she’s a beauty, too."

"I don't care about your taste in women! Honestly... wait, hold on! Did you just say 'both families'? What does that mean!?"

Yurika had been tuning her father out, but she suddenly caught a phrase that made her expression shift.

"Oh, did I not mention it? Emiko-san has a son... he’s in the upper grades of elementary school, I think..."

"Whaaaaaaaat?! I didn't hear anything about that! No way! I absolutely refuse to accept this!"

"Now, now, it's a bit late for that. He's still a small child, so it'll be fine."

"It's not 'a bit late'! I’ve been against this from the start! And it doesn't matter if he's small or not!"

"Uugh, this is trouble..." Mikiya groaned.

Full of anxiety about the future, the two of them entered the family restaurant. At this rate, the remarriage talk was about to be scrapped entirely.

Upon entering the restaurant and heading to their reserved table, they found the other family already seated. Seeing the two of them, the woman stood up.

"Hello, nice to meet you. I'm Emiko, the one seeing Mikiya-san. I really want to get along with you, Yurika-san, so I look forward to our time together."

"Ah... yes... hello..."

Yurika had intended to give the woman a piece of her mind as soon as they met, but seeing her in person, she truly did seem like a kind woman. The complaints she had prepared died in her throat.

"Um, and this is my son, Yuu. He's a fifth grader. I’d be so happy if you two could become friends."

There was a boy sitting next to the woman. This was Yuu, the boy who was supposed to become her brother.

Zkyuuuuuuuuuuuuuuuun!!!!

In that instant, Yurika’s 『one-shota heart』 was shot through!

She had always been bad with boys her own age and had a faint suspicion that she preferred younger boys, but seeing Yuu turned that suspicion into absolute certainty.

A love for "shota"—

It was a maze of love from which there was no return. A cycle of reincarnation with no exit. A prison of love where the heart is held captive. Yurika’s brain had been completely hijacked by "one-shota lovey-dovey mode."

(H-hawawawa! H-he’s so cuuuuuute! That serious, unspoiled look! What is this?! What is this?! He’s totally my type! His hair looks so silky; it looks like it would feel amazing to pet it!)

Yurika was in ecstasy.

(I-it’s okay if I touch him just a little, right? Wait! Is this a crime? Ah, that’s right! If our parents get married and we become family, I can pet him all I want! That makes it safe, right!)

※ It is not safe.

Forgetting her opposition to the remarriage, Yurika’s head was now filled with thoughts of the boy before her.

And for the other party involved, Yuu—

Zkyuuuuuuuuuuuuuuuun!!!!

In that instant, Yuu’s 『one-shota heart』 was shot through!

The truth was, Yuu was a kid who secretly loved "older sister" characters, hiding his stash of sister-moe anime and manga from his parents. He was a true "I-love-big-sisters" boy!

By the way, some of his favorites included manga and anime like The Manager of Otohime Dorm and The Gal Onee-chan is Attacking.

He had always recognized his own preference for older women, but seeing Yurika turned that into a conviction.

A love for "onee-san"—

It was the yearning for older women that every boy dreamed of. The kindergarten teacher, the older girl next door. The bittersweet memories that smelled like a first love. Yuu’s brain was now completely hijacked by "one-shota lovey-dovey mode."

(Waaaaah! She’s such a beautiful Onee-chan! Ugh, s-she's so cute, so pretty, so cool... s-she's gorgeous...)

Yuu’s eyes kept darting toward Yurika. Specifically, her chest.

(Uuuugh, I’m so nervous that someone this beautiful is going to be my Onee-chan... Her boobs are so huge...)

In her school uniform, Yurika’s chest was prominently thrust forward. It was only natural that his eyes would be drawn there.

(Ah, no! I shouldn't look! Uugh, just a little... But if I touch them, will the policemen arrest me? Ah, that’s right! If our parents get married and we become family, then it's safe!)

※ It is not safe.

Forgetting his anxiety about his mother's remarriage, Yuu’s head was now filled with thoughts of the beautiful older girl before him.

Thanks to Yurika becoming quiet, the meeting proceeded smoothly. It looked like the talk was going to reach a successful conclusion. As for Yurika, she was busy making stern, serious faces every so often to make sure her father and the others didn't realize her expression was melting into a grin. All while stealing glances at Yuu.

(Hehehe, so cute...)

He was completely locked in her sights.

Naturally, Yuu was the same. While sitting politely in his chair, he would occasionally shift his gaze toward Yurika’s face and chest.

(Uugh, this Onee-chan is incredibly cute. But if I look too much, she’ll notice. I need to cool my head.)

He was completely enthralled.

Stand!

Suddenly, Yuu stood up and grabbed his glass. Noticing this, Emiko spoke up.

"Yuu, what's wrong?"

"Getting a refill at the drink bar."

As Yuu went to get his drink alone, Yurika stood up as if to follow him.

"Oh, I’ll get a drink too. Um, I’ll keep an eye on Yuu-kun, so you two please continue your conversation."

At Yurika’s words, Mikiya and Emiko’s faces naturally relaxed.

"Oh, Yurika, that’s a big help."

"Thank you, Yurika-san. My, you’re already acting like a fine older sister."

"No, it’s nothing much."

Leaving Mikiya and Emiko behind, Yurika headed to the drink bar with Yuu. To Yurika, this was the perfect chance to be alone with him. She intended to use this opportunity to close the distance between them.

(Ufufu! It’s hard to talk in front of the parents, so now that we’re alone, I’m going to talk to him about all sorts of things!)

Yuu was hesitating in front of the drink bar. Yurika wasn't about to miss that chance. She moved in behind him.

"Hey, Yuu-kun. What kind of juice do you like?"

"Eh? Um, c-coffee, I guess..."

Yuu had clearly been about to pour something from the juice dispenser, but upon seeing Yurika’s face, he blurted out "coffee." He was likely at that age where he wanted to act a bit more grown-up.

Yurika held back a laugh, finding it endearing.

"Ehhh? Coffee is bitter, you know. Can you really drink it, Yuu-kun?"

"I-I can! And I’m not a kid anymore."

"Fufu, he said 'I'm not a kid'... so cute... (whisper)"

"Hm? Did you say something?"

"Nothing at all. Yuu-kun, the hot water is dangerous, so Onee-chan will help you."

Yurika reached her arms around from behind Yuu. It was essentially a back-hug, and her large breasts squished softly against him.

"There, the coffee is this machine here. Let’s brew some."

"Uugh."

Being held in a back-hug by Yurika, Yuu felt like he was being enveloped by his dream "older sister" character, and his heart wouldn't stop pounding.

(Kuuuuuuugh! T-t-t-t-the boobs! No! If I clear my mind of all thoughts, even breasts will feel cool! If I keep thinking about perverted things, the policemen are gonna arrest me!)

Pshhhh!

Yuu’s face was beet red. Seeing this, Yurika’s expression turned mischievous.

"There, the coffee’s done. Oh my? Yuu-kun, your face is bright red. Whatever could be the matter?"

"Kuuuugh..."

Thus, their first meeting—steeped in a certain fated "one-shota" atmosphere—was a success. They had both left a powerful impression on the other's heart.

◆　◇　◆

The dinner meeting concluded, and Yurika and Mikiya were on their way home. Mikiya was stealing glances at his daughter, worried about her reaction.

"So, what do you think? She seems like a nice woman, right? I... I won't fail this time. And Yuu-kun seems like a very honest boy..."

"He’s fine."

"So, maybe you could be a bit more positive... wait, what?! 'He's fine'?"

Mikiya did a double-take at his daughter's face.

"I said he's fine. She definitely seems kind and has a good personality. She’s calm and has a nice aura. Unlike Mom, I don't think she'll be fighting all the time and tearing the family apart."

"T-thank God. Thank you. In that case, I’ll move forward with the plans."

While her father was nearly dancing with joy beside her, Yurika was dreaming of the "sweet life" with her new brother that was about to begin. She felt like she could start dancing along with him.

◆　◇　◆

The remarriage was decided without a hitch, and Yuu moved into the Akashi household.

A new life had begun. For Yuu and Yurika, it was the start of a fresh yet awkward daily routine, much like a newlywed couple's first days. It was like squeezing a sweet, succulent fruit. It was the opening curtain of a long, heated era of romantic warfare where their hearts wouldn't stop pounding, day or night.

And then, surprisingly, the newly remarried parents decided to go on their honeymoon to Hawaii immediately. A four-night, five-day trip. Mikiya turned a worried face to Yurika.

"Alright, Yurika. I'm leaving the house in your hands."

"I know, I know. I'm better at chores than you anyway."

As for Emiko, she seemed to place absolute trust in Yurika.

"Yurika-san, please look after Yuu."

"Leave it to me, Emiko-san. I will take full responsibility for raising Yuu-kun."

She was fully prepared to "raise" him. Though perhaps in a slightly different sense. Even Emiko seemed overwhelmed by her enthusiasm.

"M-my, you certainly are reliable..."

And so, leaving the house and Yuu in Yurika’s care, Mikiya and Emiko departed for their tropical resort.

Click—

The door closed, and Yurika and Yuu were alone in the house. For the next five days, this house was about to be transformed into a love nest. A nest shared by two people who were each other's absolute favorite type.

(Hehehe! Alone with Yuu-kun! Opportunity knocks! Heh-hey-hey!)

Yurika shouted a strange cheer in her mind. Despite her being a top-tier beauty, her personality was... well, a bit "off."

"Hey, hey, Yuu-kun. What do you want to play?"

"Ugh... I-I’m gonna play by myself."

"Ehhhh?! Let's play together!"

"I'm gonna play games in my room."

Yuu gave her a curt response and headed back to his room. While he was incredibly interested in his beautiful older sister, he was so embarrassed that he ended up doing the exact opposite of what he actually wanted—which was for her to pay attention to him. He had no idea that his "tsundere" boyish heart only made Yurika more eager to tease him.

"Whew... that was nerve-wracking..."

Slumping down on the floor of his room, Yuu let out a breath and started up his game.

"Damn it! That Onee-chan is too sexy. Her boobs jiggle every time she talks..."

To an adolescent Yuu, the pheromone-radiating Yurika was too much stimulation. You might think it's impossible for breasts to jiggle that conveniently, but that was only because Yurika was intentionally making them jiggle whenever she was in front of Yuu. Yuu, oblivious to her tactics, was left flustered by the constantly bouncing assets.

"Ugh, looking at her makes me want to do 'bad things.' I have to stop looking at her."

Of course, Yurika was about to launch a full-scale offensive.

Knock, knock!

"Yuu-kun, I brought some snacks~"

Hearing Yurika’s voice from the hallway, Yuu straightened his posture.

"Whoa, here she comes!"

Click!

Carrying snacks and tea, Yurika invaded Yuu's room. This was the Yurika Style: Art of War.

【Fast as a Carnivorous Onee-chan】

【Quiet as a Refined Onee-chan】

【Aggressive as a Lewd Onee-chan】

【Immovable as a Tsundere Onee-chan】

With this strategy, Yurika had won 130 out of 130 battles in her mental simulations. She was the undefeated, invincible Onee-chan. However, since she had zero actual experience, no one knew if she was actually strong or not.

By the way—

【Mysterious as a Sage Onee-chan】

【Active as a Yandere Onee-chan】

...there was more to the strategy.

"Yuu-kun, what are you doing?"

Yurika peered at the screen of Yuu's smartphone game, leaning in so that their shoulders touched. Yuu could feel her body heat, and the sweet scent of her shampoo wafted over him.

(Uugh... she smells so good... She’s so sweet and soft... N-no! This is too much!)

Seeing Yuu's embarrassed face, Yurika leaned in even closer.

"Hey, hey, what kind of game is this? Tell Onee-chan about it!"

"Uugh... uuuugh..."

Yuu’s face turned beet red, all the way to his ears. As for Yurika, seeing his innocent reaction made her heart skip a beat, and her possessiveness and desire for dominance started to reach dangerous levels.

(Ufufu! Yuu-kun is turning bright red, how cute! Hehehe, it makes me want to flirt even more!)

Despite being a "giggle-giggle" pervert sister on the inside, she didn't show it and kept a gentle smile on her face.

"Hmm, so Yuu-kun likes this kind of character?"

Squish! Squoosh!

Yurika was now hugging Yuu from behind. Not just her shoulders, but her soft curves were pressing against him.

"Waaaaah! Enough! Go away already!"

Perhaps she had gone too far; Yuu pulled away and moved over to his desk.

"Che, what’s the big deal? Just a little bit is fine."

Yurika complained, sounding frustrated. It seemed Yuu was determined to focus on his game and wouldn't pay her any mind.

"Hmm, well, if that’s how it is..."

Left with no other choice, Yurika began to rummage through the room. She wanted to know her cute step-brother's hobbies, after all.

(Emiko-san did ask me to look after Yuu-kun, after all. I need to check his hobbies and fetishes.)

No one had asked her to check his fetishes.

"Let’s see..."

Standing in front of the bookshelf, she glanced at the titles of the manga and light novels. Yuu was too absorbed in his game to notice.

(Now’s my chance! Boys always double-stack their bookshelves and hide the perverted stuff in the back!)

Yurika pulled out a few Shonen manga from the front row to check what was hidden behind them. For some reason, she had a sharp nose for finding erotic material. Just because she hid her own perverted books in the back didn't mean everyone else did, though.

"Ah..."

There actually was erotic material in the back of the bookshelf. It wasn't hardcore 18+ stuff, but it was slightly "ecchi" Seinen rom-coms.

"Ehhh... whaaa...?"

The problem was the titles. Yurika suddenly became flustered. She had seen something she shouldn't have, and she was suddenly overcome with embarrassment.

"A-anyway, Yuu-kun... Onee-chan is going back to her room."

"Okay."

Slam!

Once back in her room, Yurika writhed and twisted her body as she recalled the titles of those slightly perverted manga.

"What was that?! What was that?! This is bad, this is bad, this is so bad!"

The titles of the manga hidden in the back were: My Girlfriend is My Step-Sister, The Forbidden Relationship with my Lewd Onee-chan, The Manager of Otohime Dorm, and The Gal Onee-chan is Attacking.

Yurika had burned every single word of those titles into her memory.

"T-those... those mean... Yuu-kun likes older sisters! A-a-and he’s reading erotic rom-coms about step-sisters... T-t-t-that means... he’s aiming for me!"

She had been the one on the offensive with her "Art of War" earlier, but as soon as she realized her brother had a "Sister Moe" fetish, she became incredibly weak. This was all because she had zero real experience and her delusions were ten times stronger than reality.

Yes, this woman—despite looking incredibly sexy and experienced—was actually a total virgin with zero romantic history.

"Uuuugh, Yuu-kun... to think you were looking at me with such perverted eyes... I-I won't lose! I have to show him the dignity of an older sister!"

How she had arrived at this conclusion was anyone's guess. To show her sisterly dignity and adult composure, Yurika decided she would push herself to seduce Yuu and make him hers.

"Fufu... fufufu... hehehe! We’re siblings, after all. A little bit is fine! It's safe, right!"

※ It is not safe.

◆　◇　◆

Night came, and the two of them sat down for dinner. Since her biological mother had left, Yurika had been doing all the chores, so cooking was one of her specialties. She had whipped up a quick curry with the ingredients in the fridge and served it to Yuu.

"Yuu-kun, how does it taste?" Yurika asked, sounding a bit nervous.

"U-u-uuu..."

"U?"

"I-it’s good!"

"Really?! I'm so happy~"

Seeing Yuu gobbling down the curry, Yurika's face naturally brightened.

"It’s really delicious... munch."

Growing up in a single-parent household, Yuu hadn't often eaten fresh, homemade meals. He had made some himself occasionally, but it was like night and day compared to Yurika’s curry. Eating a meal cooked with love for the first time in a long while, Yuu felt a gentle, happy warmth.

(This Onee-chan... she’s not just an annoying, sexy sister...)

While his thought was a bit rude, for Yuu—who had been starved of familial affection—the presence of this beautiful and cute step-sister was starting to become very important.

"Yuu-kun, how about now? Do you have a better opinion of me?"

"A little."

"Ehhh? Only a little?"

"Okay, a bit more than a little."

Despite saying "a little," Yuu had actually gained a massive amount of respect for Yurika.

(It’s really good. Did she make this just for me?)

He had been captivated by her at first sight, but her subsequent "annoying" attacks had put him off a bit. However, it was only natural for his "I-love-big-sisters" feelings to resurface for a sister who looked after him so kindly.

◆　◇　◆

"Yuu-kun, why don't you hop in the bath first?"

"Okaaay."

Having finished dinner, Yuu was relaxing in the living room when Yurika nudged him toward the bathroom.

Lowering his guard completely, Yuu stripped down in the changing area and stepped into the bathroom alone.

"Phew... I was wondering how things would go, being alone with a Onee-chan that sexy, but it looks like we’re actually gonna get along fine. Guess I won't be getting arrested by the polis-men after all," he muttered to himself.

Stretching out as he soaked in the tub, he whispered his honest feelings about his sudden new sister. For a boy his age, even if a woman that alluring and erotic was presented as a "sister," it wasn't easy to just accept it—he was usually too busy being flustered and excited.

However, after experiencing Yurika’s genuine kindness, Yuu’s heart was beginning to thaw.

But just as he was starting to think life with his new family would be smooth sailing, a storm arrived to shatter that notion. Specifically, his sister barging in.

Rattle-clatter!

"Yuu-kuuun! Let's soak together!♡"

Yurika charged into the bathroom without a single stitch of clothing on.

In other words, she was buck naked!

"W-w-w-wha—! Why are you coming in here!?"

"Well, I mean... you know how it goes with newlyweds! 『Darling, would you like dinner? A bath? Or... m-e?』 Just kidding~!"

Yuu had no idea what was supposed to be "just kidding" about it, but Yurika’s erotic offensive had officially gone off the rails.

A sweet home for just the two of them. A sanctuary like the bath. Facing an invasion from his "dirty" sister while completely defenseless, Yuu’s life as a virgin was hanging by a thread.

Her beautiful, provocative body rose out of the steam. Her skin was moist, firm, white, and translucent. Right there in front of Yuu was his idolized step-sister in her birthday suit.

Boing!

Two soft mounds that seemed to defy gravity pointed proudly upward. The flowing curves led from her stomach to her waist, followed by the rounded, perfectly shaped swell of her rear. And then there were her legs—fleshy and curvaceous, yet perfectly toned.

It was the ideal physique: explosive where it needed to be, and tightly cinched where it counted.

"Ugh... boobs... butt..."

Yuu was speechless, his eyes glued to Yurika’s body. It was as if a seductive "Onee-san" character had stepped right out of a manga and descended before him.

"Yuu-kun! Let's get in together!"

"Waaaaah! Don't come any closer! Go away!"

Terrified by the advancing sister, Yuu covered his eyes with both hands and backed away, trying not to look at her nakedness. Of course, he was actually burning every detail into his memory through the gaps in his fingers.

(She's a total disaster of a sister!)

There was no escape for the cornered Yuu; his erotic sister’s bountiful chest was closing in mercilessly.

"Come on, Yuu-kun! Let Onee-chan wash your back for you~"

"P-put some clothes on!"

"It’s a bath, of course I’m naked. You’re being weird, Yuu-kun."

"You’re the weird one here! A-at least use a towel!"

"Jeez, you're such a handful, Yuu-kun."

Since Yuu was so insistent, Yurika compromised by wrapping herself in a towel. However, for some reason, the one she chose wasn't a bath towel, but a small face towel. Her "explosive" body couldn't even begin to be hidden by such a tiny scrap of fabric.

"There, I’ll wash your back. Sit, sit."

After lathering up some body soap, Yurika began to wash Yuu's back—not with a sponge or a towel, but with her bare hands.

Squish... slide... squelch... rub...

"Ugh! Ah! Wait! T-that tickles!"

"Stay still, or I can't wash you properly."

"B-but... why are you using your hands?"

"Washing with your hands is better for the health of your skin."

While it’s true that hand-washing is supposedly gentler on the skin, in Yurika’s case, her motives were highly suspect.

(Hehehe! Yuu-kun’s skin is so smooth! He’s squirming around... so cute!)

Meanwhile, Yuu was at his breaking point from all the things his dream "Onee-san" was doing to him.

(D-damn it! This feels too good! I can’t hold back anymore! Everything is being reflected in the mirror in front of me! That towel isn't hiding a single thing!)

Indeed, the mirror showed everything. Yurika’s chest and rear, which the towel couldn't possibly contain, were in full view. Because the towel was so small, her cleavage and the curve of her hips were completely exposed.

Slide... squelch...

Yurika’s hands slipped from Yuu’s back around to his stomach.

"Whoa! Stop! If you do 'lewd things,' the polis-men will—!"

"Eh? What are 'polis-men'? Do you mean the police? If so, I’ll just become a super mini-skirted policewoman and arrest my perverted Yuu-kun as quickly as possible!"

"Waaaaaah!"

Against Yurika, the world’s strongest sister, neither the state’s authority nor the US military stood a chance.

However, as Yuu neared his limit from his sister’s excessive skinship, Yurika’s own excitement was reaching a dangerous, fever pitch.

(Yuu-kun looks like he’s enjoying it. Maybe just a little... further down front...)

Her hands grew increasingly suggestive, looking as if she were about to wash some very dangerous places.

"Yuu-kun, should I wash the front, too?"

Just as the excited Yurika was about to stand up, her foot slipped on the wet floor, and she lunged forward, hugging Yuu with all her might. Her hand accidentally clamped down right on his "forbidden" area.

"Kyaa!"

"Waaaah! D-don't touch me there!"

Clonck!

Yurika’s hand was firmly cupping Yuu’s most important asset.

"Eh? A-ah... Yuu-kun... I-I'm sorry!"

"U-uuuugh... waaaaaaah! I hate you! I hate you so much!"

Yuu bolted out of the bathroom.

Left alone, Yurika stood there in a daze, Yuu's scream echoing in her head.

I hate you! I hate you! I hate you!

Yurika’s face turned pale.

"U-uwaaaaaah! I made Yuu-kun mad! What am I gonna dooooo!?"

◆　◇　◆

And so, their first "bathing together" event ended in a cloud of awkwardness. Yurika, unable to recover from the shock of making Yuu angry, slunk into the living room with slumped shoulders.

"Y-Yuu-kun, I’m sorry about earlier."

"Hmph."

Yurika opened the fridge and grabbed some ice cream.

"U-um, Yuu-kun, do you want some ice cream?"

"Hmph."

She spoke to his back, but he didn't budge.

"Yuu-kun..."

"Hmph."

Without a word, Yuu headed upstairs to his room.

"Waaaaaaah! He really hates me! What am I gonna dooooo!"

Back in her own room, Yurika collapsed onto her bed, flailing her legs and clutching her head in agony. She had gone too far, following her instincts with her new, perfectly-to-her-liking step-brother. While she wanted to dote on him and look after him, there was no denying that a few "ecchi" feelings had been mixed in.

Trust is hard to build, but it only takes an instant to destroy.

"I-I-It’s not destroyed yet!"

A flustered Yurika snapped at the narrator-like voice in her head.

"Yuu-kun... I didn't mean to make you mad..."

Tears welled up in Yurika’s large, beautiful eyes.

"What do I do... waaaaah!"

Meanwhile, inside the room Yuu had fled to—

"Waaaaaaah! She found out I was looking at her with perverted eyes! What am I gonna dooooo!"

The truth was, he wasn't angry at all; he was just so embarrassed that he couldn't look his sister in the eye.

"She definitely noticed... Her hand hit it after all."

He had been stealing glances at the parts of Yurika—her chest, her rear—that the towel couldn't hide in the mirror. He was terrified that when she hugged him and touched him, she had realized he was actually turned on.

"I can't take this anymore..."

Faced with his incredibly cute and perfect new sister, his body had reacted instinctively. While he wanted her to spoil him, there was no denying that he also wanted more "ecchi" skinship.

Trust is hard to build, but it will crumble if you only look at someone with perverted eyes.

"I-I-I wasn't being perverted! O-okay, maybe I was, but...!"

A confused Yuu tried to snap at the narrator-like voice, but he stopped because, yeah, he had been being a total pervert.

Click!

As Yuu left his room to use the restroom, he bumped right into Yurika. It was a stiff, awkward confrontation in the wake of their "fight."

Yuu looked at Yurika’s face and thought:

(Ugh... I have to apologize... But I can’t exactly say, 'Sorry, I was looking at you with lewd eyes and got a bit excited.')

Yurika looked at Yuu's face and thought:

(Ah... I have to apologize... But I can't exactly say, 'Sorry, I was pretending to look after you when I actually had perverted feelings.')

They were two of a kind.

"Um..."

Their voices overlapped.

"Y-you go first. I don't mind."

"T-then... I'll say it."

Fidgeting, Yurika put on a serious face and began to speak.

"U-um... about earlier... I-I'm sorry!"

"Eh?"

"I-I didn't mean to touch you there. My hand just slipped... it was an accident... (even though I was about 50% perverted)."

"U-um, yeah."

"I just wanted to get closer to you, Yuu-kun. That’s why I tried to wash your back... (even though I was about 75% perverted)."

"Yeah..."

"So, I want to make up with you, Yuu-kun."

Yurika expressed her honest feelings. Of course, she kept the perverted part hidden.

"Yeah, let’s make up."

"Really? You’re not mad anymore, Yuu-kun?"

"I wasn't mad... I was just embarrassed..."

"I see! Thank goodness~!"

The two of them successfully made up. It was a beautiful display of sibling love—or so one might think...

"By the way, Yuu-kun... stop calling me 'you' and start calling me 'Onee-chan' properly."

"Ugh... n-no way."

"Ehhhhh?!"

As a massive "Siscon," Yuu desperately wanted to spoil his sister, but he was too embarrassed to actually do it.

"Oh... that reminds me. Yuu-kun, you were stealing glances at my naked body and getting exci—"

"Waaaaah! Okay, okay! I’ll say it! Onee-chan!"

"There we go! Good boy~"

Yurika beamed with a radiant smile, while Yuu was shaking in his boots.

(Ugh... this sister... I thought she was just a lewd "Onee-san," but maybe she’s actually a terrifying woman...)

"Then, as a sign of our reconciliation... let's sleep together tonight!♡"

"WHAAAAAAAAT!?"

Yurika had once again blurted out something outrageous. For a boy in the middle of puberty to sleep with an "ecchi" sister like her... he’d be so excited he wouldn't get a wink of sleep. It was basically torture.

"There's no way I'm doing that!"

Yurika’s eyes glinted as she looked at the protesting Yuu.

"Hmm, I guess Yuu-kun is being a bad boy. Maybe I should mention those perverted books in the back of your bookshelf..."

"Waaaaah! Okay! I'll sleep with you! Please let me sleep with you, Onee-chan!"

"There we go! Good boy~"

Yurika seemed satisfied with Yuu's obedient reply. It seemed Yuu was slowly being "trained." In a single day, he had been saddled with all sorts of weaknesses.

Meanwhile, Yurika, who had been depressed thinking Yuu hated her, had managed to flip the script in an instant. She truly was the world’s strongest sister.

"Come on, let's go to bed! We’re siblings, so it’s safe, right!?"

※ It is not safe.

And so, Yuu ended up sleeping beside a step-sister so sexy you could almost see her pheromones. Could Yuu survive a night with this "lewd" sister and her overflowing erotic aura?

A long night was about to begin.

◆　◇　◆

Late at night in their sweet home for two.

Yuu, having been dragged into the bed in Yurika’s room, was being hugged by the pheromone-leaking Yurika. Her soft breasts and fleshy thighs were pressing against him everywhere.

"Mnn... ahhh... Yuu-kuuuun..."

"Whoa! Don't hug me so tight!"

Whether she was doing it on purpose or just sleep-talking, Yurika was clinging to him so tightly he couldn't relax. She was playing a dangerous game on the line between "intentionally touching" and "accidentally bumping into him." Yuu didn't even know if he should wake her up to complain.

(Ugh... this is too much. I can’t take this...)

Yurika’s arms and legs were pressing against some very sensitive spots. If his excitement reached its limit, something terrible might happen under the covers.

"I can't do this anymore!"

Yuu sat up and pried his erotic sister’s legs off him. To sleep through all that... she must be an incredibly bold woman, he thought.

"Phew... finally free."

As he caught his breath, his eyes fell upon Yurika, whose pajamas were in disarray. Her pale skin was exposed where the fabric had shifted, and Yuu instinctively swallowed hard.

Gulp...

Her soft-looking stomach was in full view, and if the fabric shifted just a bit more, he might see the underside of her breasts.

(N-no! She’s my sister now, even if we aren't blood-related! More importantly... looking at a sleeping girl like this is totally wrong.)

Yuu tried to fix his step-sister’s messy pajamas for her. However, the moment he grabbed the hem, he lost the battle against the magic of her alluring, smooth skin.

"Ugh... just a little peek..."

He lowered his head slightly, trying to glimpse her breasts through the gap in her pajamas—

"Yuu-kun, what are you doing?♡"

"Waaaaah!"

Yuu looked up to see Yurika staring at him with a smirking face.

"T-this isn't... I mean... your pajamas were..."

"Oh, were you trying to fix them for me?"

"Y-yeah, exactly! I didn't want your stomach to get cold..."

"Thanks, Yuu-kun. You’re so kind."

"Y-yeah..."

Yurika gently hugged Yuu’s shoulders and leaned in close to his ear.

"Pervert."

"Ugh...!"

She had seen right through him.

That night, as a punishment, he was sentenced to be her "body pillow" and spent the rest of the night being squeezed tight.

"Ahhh... Yuu-kuuuun... mumble mumble..."

"Waaaaah! Stop it!"

He could feel Yurika’s soft texture clearly through their clinging bodies. Wrapped in her dizzying scent and warmth, it felt as if he were being disciplined by her curvy, seductive body itself.

"Ahhh, Yuu-kun..."

Her wandering hands kept slipping into various places—his sides, even between his thighs. For an adolescent boy to be teased like this indefinitely... it was unbearable.

"What is this nightmare!?"

As Yurika slept soundly using Yuu as a pillow, and Yuu stayed awake, agonizingly excited, the two continued their silent battle in bed until dawn broke.

The next morning, Yurika woke up and gave a long stretch.

"Mnnnn! I slept so well~!"

Meanwhile, Yuu was suffering from a massive lack of sleep after being clung to by her fleshy limbs all night.

"Ugh... I didn't sleep at all..."

Having large breasts pressed against him and legs tucked between his... it was only natural he couldn't sleep. It was a "punishment" that made him never want to sleep together again.

And so, their days of happiness, eroticism, and agony continued to flow.

◆　◇　◆

The morning of the last day of the long weekend. Yuu and Yurika were eating breakfast together.

"Hey, Yuu-kun. School starts tomorrow, are you gonna be okay? Do you want Onee-chan to walk you there?"

"No, I’ll be fine."

Yuu took a bite of his toast, answering immediately to Yurika’s overprotective aura.

Because of the move, Yuu had transferred schools. Tomorrow would be his first day. Yurika was having the time of her life living with Yuu, but she occasionally felt a pang of guilt or sadness, wondering if he missed the friends he had left behind.

(I wonder if Yuu-kun will be okay... I’m so worried... What if he gets bullied at school? I’m so worried I might go crazy...)

Ping!

An idea flashed in Yurika’s head.

(That’s it! If I become a teacher at Yuu-kun’s school, I can look after him at home and at school all day long!)

The truth was, Yurika was planning to enroll in the faculty of education. She had vaguely thought about getting her teaching license and becoming a teacher, but meeting Yuu had given that goal a concrete purpose.

Plus, she was already fantasizing about giving Yuu all sorts of (forbidden) "education."

(Hehehe! It’s my 'Reverse Tale of Genji' plan! Just as Hikaru Genji raised young Murasaki into his ideal woman, I’ll educate Yuu-kun into my ideal boy...♡)

T/N: Referencing the Tale of Genji, where the protagonist raises a girl to be his perfect wife. A "Reverse" plan implies Yurika is "raising" Yuu to be her perfect husband.

Yurika was becoming a bit dangerous.

"Still, I'm glad the university is close enough to commute from home," she mused aloud, her delusions leaking out.

Yuu, caught off guard by the sudden comment, looked at her blankly.

"You haven't even taken the entrance exams yet. You’re already acting like you passed?"

"I might as well have. Your Onee-chan is the strongest, after all."

It was a nonsensical claim, but for some reason, Yuu felt she had the power to make it a reality. To him, the step-sister before him looked like a cute, invincible sister straight out of a manga.

Yurika’s expression softened as if she had just thought of something.

"Hey, Yuu-kun. Let's go out to the city today!"

"I’m gonna play games at home."

"Ehhhh! Let's go!"

"No."

Yuu gave a curt reply, but the truth was, he desperately wanted to go out with his sister.

(Ugh, I want to go. I really want to go, but it’s embarrassing. She’s probably gonna be all clingy in public...)

But Yurika was one step ahead.

"Oh, that’s right... I heard Wac-Wac Burger is doing a limited-time 『Butt Burger』 and a Chestnut Shake. Maybe Onee-chan should treat you?"

"Ugh... the Butt Burger and Chestnut Shake... gulp..."

Hearing about the Wac-Wac limited menu, Yuu started to get fidgety.

A new limited-time product from the popular hamburger chain, 『Wac-Wac Burger』. It featured a round, voluminous bun designed to look like a beautiful rear end, sandwiching a luxurious 100% beef patty.

When you bit into it, something thick and dark... the juicy patty... would pop out from between the "cheeks," which had led to some internet outrage calling the item "obscene."

The other item, the Chestnut Shake, was just a popular autumn flavor. It didn't have any suggestive meaning. Probably.

Yuu was embarrassed, but he couldn't resist the allure of the limited burger and shake.

"The Butt Burger and Chestnut Shake... I'll go."

"Yay! Let's head out then!"

Lured by food, Yuu easily agreed to the outing. Yurika immediately began her preparations.

"Hey, Yuu-kun. Which of my outfits do you like best?"

As she spoke, Yurika started to strip.

"I told you, stop taking your clothes off!"

"I can't change if I don't take them off. You’re being weird, Yuu-kun."

"You’re the weird one! Put some clothes on!"

"Jeez, you're such a handful. Also, stop calling me 'you'! Call me 'Onee-chan'!"

Yurika was completely unfazed by the flustered Yuu. Just catching glimpses of her white underwear made Yuu's heart race. In just a few days, he had been completely captivated by Yurika’s charm.

"Do you like me in my school uniform better than my civilian clothes? You do, don't you!?"

The outfit Yurika chose was her high school uniform—a cute blazer-style design. Yuu was instantly captivated.

(Ugh, she’s so cute. She was amazing when we first met, too. Is she trying to turn me into a uniform fetishist?)

In her uniform, Yurika’s cuteness was doubled. Her large breasts strained against her blouse, and her short skirt generously exposed her smooth thighs. Yuu began to worry that if such a cute sister rode the train or walked around the city, she’d surely be targeted by some degenerate groper.

With his boyish heart, he swore an oath: (I have to protect my sister!)

When they finished changing and stepped out of the house, a woman Yuu didn't recognize was standing there. She was a middle-aged woman who looked somewhat like Yurika. She was dressed in flashy fashion and had a slightly harsh expression on her face.

"Yurika, it's been a while."

"Mom... I mean... what are you doing here...?"

Yurika, who always had a kind smile, now looked like she was enduring something painful.

"Mom...?" Yuu echoed.

"Oh, is Mikiya not here? I have some business with him."

The middle-aged woman gave Yuu a brief glance before speaking in a high-handed manner.

"Mom... I told you not to come here anymore."

"Hah? What an impudent daughter! I’ll do whatever I please!"

"Ugh..."

It seemed she was Yurika’s biological mother. Even from their brief exchange, it was clear their relationship was toxic. Ignoring Yuu’s presence, the woman made a shameless demand.

"Well, you’ll do. Give me some money! That man is making decent money, isn't he? You should help me out a little!"

"T-that’s not true... Do you have any idea how much Dad struggled...? He worked himself to the bone to pay off the debts you made, and we finally managed to live a normal life... And now he’s remarried and finally supposed to be happy!"

Hearing the word "remarried," the woman’s eyebrows twitched.

"Hmph, so he remarried. I wonder what anyone sees in such a plain, boring man. But I won't let Mikiya be the only one who gets to be happy! If you won't lend me money, I'll tear it all down."

Suddenly, the woman fixed her gaze on Yuu.

"Is this boy the child of the person he remarried? You’d better be careful! Yurika has the same 'playgirl' blood in her veins that I do. I bet she's already causing trouble at school, playing around with men. She’ll just end up being a burden on you, too. Ahahahaha!"

Her laughter echoed in the entryway. Yurika felt as if the world were turning black. She had finally escaped her troublemaking mother and started a stable life. She had been planning to live a happy, peaceful life with her new favorite step-brother. Why did this woman always have to come and interfere?

The term "parent lottery" was popular these days, but thinking that her own mother was such a person filled her with unbearable sadness.

She had cheated repeatedly, racked up debts, and left with another man, yet since her second divorce, she had frequently come crawling back for money. She would scream and shout if things didn't go her way, causing nothing but misery.

Was that still not enough for her?

(Mom, how much more of my life are you going to ruin...)

Unaware of her daughter's feelings, the mother pressed her further.

"I said give me the money, now! Honestly, if you have money to play around with men, you should spend it on your mother! Hurry up, you useless girl!"

Just as the mother was about to raise her hand, Yuu stepped in front of Yurika to protect her.

"Stop it!"

He spread his small hands wide and glared straight at the woman.

"Hah? What is this brat? This doesn't involve you! Move!"

"It does involve me! My sister is family! I have a duty to protect my family!"

Yuu puffed out his chest and proudly declared Yurika to be his family.

"What did you say?! I'm this girl's mother!"

Despite the woman’s bristling anger, Yuu didn't flinch.

"You’re not a parent! Why... why... even though you’re a mother, do you only do things that hurt your daughter!? I’m not saying every parent has to live solely for their children! But all you do is cause her trouble! My sister is nothing like you! She’s kind, helpful, beautiful... anyway, she’s completely different from you! Now get lost, you shitty old hag!"

"What did you say!? B-B-B-Old hag!? Why, you little brat! I have a name, and it’s Rieko!"

"I called you an old hag because you’re an old hag! Hag!"

"Don't you look down on me! You’re just a kid!"

Yuu took another step forward.

"I might be small now, but I'm gonna grow up fast! And as long as I’m here, I won't let you get anywhere near my sister! I’m going to protect her!"

Yuu declared it boldly. He would protect Yurika. He was still small, but in a few years, he would surely tower over the woman before him. The mother, who had acted with such reckless abandon until now, would no longer be able to have her way as long as Yuu was around.

Yuu swore a deep oath in his heart that he would never let his sister feel sad again.

"Ugh... y-you’d better remember this!"

With a parting shot, Yurika’s biological mother fled.

And so, the two of them were left alone in the entryway.

"U-uuuugh... waaaaaaaaah! Yuu-kuuuuuun! Thank youuuuuuu!"

Yurika burst into tears, the droplets falling thick and fast. To think her cute, young step-brother would actually protect her... A warm light kindled in the depths of Yurika’s heart. It was a powerful, bright sensation that spread through her entire body.

"If she ever comes back, I'll chase her off again!"

Seeing Yuu with his shoulders squared, Yurika couldn't help but let out a watery giggle.

"Pfft... fufu..."

"D-don't laugh! What are you laughing at!?"

"Because... Yuu-kun is just too cute! But... thank you sho mush... sniff... hic!"

"Whoa! Don't get snot on my shirt!"

Yurika buried her face in Yuu’s shirt and sobbed, even as she smiled. She soaked his shirt with tears and... all sorts of other fluids.

After clinging to Yuu for a while, Yurika finally seemed to calm down.

"Right! Let's go to Wac-Wac, Yuu-kun!"

Despite her heavy crying moments ago, she was now fully recovered. In fact, she seemed even more energetic than before. Perhaps her feelings for Yuu had shifted. After seeing him protect her, he had transitioned from just a "cute favorite" into someone she viewed as a member of the opposite sex. She was already at the "I-love-my-little-brother" stage.

"Ehehe~♡"

"Honestly, you’re such a handful."

In the end, Yuu had to change into a fresh shirt since his old one was soaked. He never imagined she would cry that much.

"Jeez, Yuu-kun, you're so cute when you try to act like an adult."

"I told you, don't get so close!"

Linking arms, the two of them headed out into the city.

◆　◇　◆

Arriving at Wac-Wac, they ordered the Butt Burger, fries, and Chestnut Shakes. Led by Yurika, they went up to the second floor and headed for a corner table hidden behind a pillar.

"Let’s sit here."

As she spoke, Yurika sat right next to Yuu.

"W-why are you sitting next to me? Usually, people sit across from each other."

"It’s a rule that close siblings sit side-by-side."

"That’s news to me..."

"Jeez, Yuu-kun. You have to listen to what your Onee-chan says."

Ignoring Yuu’s complaints, Yurika pressed her body against his, just like a lover would.

"Here, it’s the butt you love so much, Yuu-kun."

Yurika picked up the Butt Burger and looked at Yuu with a meaningful expression.

"Wait a second! Who said I like butts!? It's the Butt Burger!"

"Ehhh? But Yuu-kun, you were stealing glances at my butt in the bath the other day, and when I was changing today, too."

"...You noticed..."

Yes, Yuu wasn't just a breast man; he was an ass man as well. He was completely captivated by Yurika’s round, artistic, and beautifully shaped rear. Yuu was the only one who thought he hadn't been caught; Yurika had seen right through him.

"Kuuugh..."

Overcome with embarrassment, Yuu hid his beet-red face behind his hands.

"Sorry, sorry, I was just teasing. Let’s eat."

"Honestly..."

Yuu tried to eat his burger, but Yurika was pressed so close to him it was difficult. It seemed she was encroaching even further into his personal space than before.

"O-Onee-chan, it’s cramped!"

"Ufufu~♡ Onee-chan will feed you! Here, say 'ahhh'."

Whether she was listening to him or not, Yurika picked up a fry and held it to his mouth.

"This is embarrassing!"

"Yuu-kun, do you know why I chose this seat?"

"Eh?"

"Look, this spot is hidden by the pillar, so you can't see it from the other tables. We can flirt as much as we want here."

The moment they had come upstairs, Yurika had identified the blind spot in the room where they could be intimate. It was practically a superpower at this point.

"Come on, hurry up. Say 'ahhh'~♡"

"Ugh... ahhh..."

Chomp.

"Ufufu! How is it? Good?"

"Yeah."

"Then, it’s Onee-chan’s turn for a reward!"

Yuu hesitated for a split second, but realizing resistance was futile, he fed her.

"Here... ahhh."

"Mmm, hehehe! Thanks, Yuu-kun~"

In a corner of the restaurant hidden from other customers, the two of them flirted and fed each other like a lovey-dovey couple. It was as if time had stopped, leaving only the two of them in their own private world.

Once they finished their burgers and fries, Yurika suddenly spoke up.

"Yuu-kun... earlier, when I was being attacked by my mother, I was so happy that you saved me."

"It was only natural."

"I always thought my life was just one failure after another. But you saved me... you called me family... and you said you’d protect me. I felt like... like I’d finally been rescued. Thank you."

"U-um, yeah."

Yurika gave him a smile that came from the bottom of her heart. Seeing her smile like a blooming flower, Yuu felt a small sense of pride that he had been able to protect his sister.