Yuna's eyes widened with a genuine, unfeigned shock, which quickly crinkled into an expression of pure, unadulterated malice.
"EW! YOU'RE DISGUSTING, BIG BRO!" she hissed, but her thighs squeezed his waist with a disturbing, enthusiastic pulse. "You want your little stepsister stinky for your perverted night visit?!"
She slid down his back, landing with a soft thud on the porch.
Just as he thought she was storming off in disgust, she whirled around and grabbed his collar, her face inches from his.
"Fine," she breathed, her voice thick with a dark, thrilling promise. "I'll skip bathing on Friday. I'll even... rub myself after Thursday's gym class."
Her grin turned feral as she pushed him toward the front door. "But if you chicken out?" She held up her phone. On the screen was a video, taken from her point of view, of him eagerly licking her cunt.
"Delete it, now! When did you take that?" he grunted, trying to grab the phone.
"Not telling." She stuck out her tongue and pulled away. "Sweet dreams! Dream of my unwashed pussy, big bro."
She skipped inside, her final words a cheerful, horrifying taunt just as their father called out a greeting from the living room.
"Come home earlier next time, you two!" their father's voice echoed, blissfully unaware of the depraved contract that had just been sealed on his doorstep.
Makoto stood frozen, his heart hammering against his ribs.
The days leading up to Friday were a special kind of torture. A gnawing guilt had taken root in Makoto's gut, a cold, heavy stone that sat there day and night.
He'd replayed the conversation in the restaurant, the deal struck on the porch, over and over in his mind.
He was a monster. A degenerate who was not just fantasizing about, but actively planning to defile his own stepsister in their family home.
He tried to avoid her. He'd leave for his part-time job before she woke up and come home long after she'd gone to her room, burying himself in work and study in a futile attempt to outrun his own conscience.
But Yuna, it seemed, had other plans. She was a hunter who had tasted blood, and she wasn't about to let her prey escape.
On Tuesday, he found a sticky note on his monitor.
"Don't forget our 'study session' on Friday night, onii-chan! I'm getting so excited, I can barely sit still in class! (´♡‿♡`)"
Beneath the cheerful text was a crude, hand-drawn picture of a bunny. It was both innocent and deeply, deeply profane.
On Wednesday, as he was grabbing a late-night snack from the kitchen, she appeared behind him like a ghost, her presence announced only by the faint scent of her strawberry shampoo.
"You're working so hard," she whispered, her voice a low purr in the quiet kitchen. He jumped, nearly dropping his onigiri.
She was wearing one of his old, oversized hoodies and a pair of tiny sleep shorts that left little to the imagination. "Is it because you're trying to earn enough to pay for our… private tutoring?"
She reached past him to grab a bottle of water from the fridge, her arm deliberately brushing against his, her breasts pressing against his back for a split, agonizing second.
"Don't worry," she murmured, her breath hot against his neck. "I'll make sure you get a passing grade."
He fled back to his room, his heart hammering, the guilt and desire churning into a toxic, irresistible cocktail in his stomach.
He was disgusted with himself. And he was harder than stone.
Thursday was the worst. He came home, utterly drained, to find the house quiet. He thought, with a surge of relief, that she was out.
He slumped onto the living room sofa, closing his eyes for just a moment.
"Tired, big bro?" Her voice came from right beside him. He flinched, his eyes snapping open.
She was curled up at the other end of the sofa, pretending to read a manga, though her eyes were fixed on him over the top of the book.
She was wearing her old school uniform, the pleated skirt riding high on her thighs.
"Mom's working late tonight," she said, her voice casual, but her eyes held a dangerous glint. "It's just us."
She uncurled herself, stretching like a cat, a slow, deliberate movement that made her white blouse strain against her breasts.
"I had gym class in college today, it was so hot and sweaty..." she announced, her voice a little too loud in the quiet room.
"Forgot my spare underwear, so I had to go commando all afternoon." She stood up and walked towards the kitchen, her hips swaying with a practiced, tantalizing rhythm.
"It was so breezy," she called back over her shoulder, a wicked smirk playing on her lips.
"You have no idea. Wanna check it?" She shook her soft ass teasingly, as if daring him to take a glance at them.
Makoto sat frozen on the sofa, his conscience screaming at him to run, to lock himself in his room, to call the whole thing off.
"I was a good person, wasn't I? A normal brother? I should be protecting her, not plotting her defilement."
But as she walked back into the room, a glass of juice in her hand, her scent—a mixture of sweat, soap, and something uniquely, intoxicatingly Yuna—wafted over to him.
His body, a traitor to his own morality, responded instantly.
The guilt was still there, a cold and hard knot in his gut. But woven through it, hot and undeniable, was a thick, coiling thread of pure, consuming lust.
He was a monster, and the monster was starving. Friday couldn't come soon enough.