Yuta sighed as he stepped inside the house. Well, he was expecting to spend all day with his friends, but now that one of them had gotten sick, they'd called it off, so he had to come home early. He was disappointed, and so he wanted to do some swimming to take his mind off of it. Grumbling all the way there, he went to his room, grabbed his bathing suit, got changed, grabbed a towel, and headed outside to their pool.

Of course, Yuta was expecting Aoi to be there using it, as she liked to when she wasn't at Hope's Peak, just to get some practice in, but what he wasn't expecting was to see her swimming…naked.

As soon as he saw it, he froze on the spot, watching as she came out of the water, her back arched, her breasts jiggling as she rose up. The water cascaded down her tanned mounds, droplets stopping on her nipples before plopping back into the water. Yuta instantly felt himself getting hard. You would think he'd feel guilty about it, considering it was his sister, but to be honest, he'd always kind of had a thing for her, at least for her body. He liked to sneak glances at it whenever he could, and even once accidentally walked in on her changing and got to see her bare chest. But that was a brief glance, this was full on in the sunlight.

She dove back into the water, her bare ass dipping up out of the water for a brief moment before she went back under. He didn't know what to do, other than just stand there in shock. It wasn't until Aoi surfaced again that she finally noticed him, and when she did, she quickly threw her body under the water, her face turning a deep scarlet.

"Y-Yuta?! I-I thought you were…"

"Plans…fell through." He said, not looking away. "What are you…?"

"A-ah! This! I…um…I just…like to swim…n-naked…sometimes…" She said. "P-please don't tell anyone!"

"I won't…" He said, and then stopped. He knew he shouldn't, but a terrible idea crossed his mind, and he couldn't resist, "…as long as you let me swim with you." Aoi went wide-eyed.

"L-like this?!" She asked, and he nodded. She sputtered. "B-but-!"

"That's my condition." He said, and Aoi scowled, looking away.

"Ugh…fine." She said. He smiled, ran up, and jumped into the pool, surprising Aoi. He only stayed under for a few moments before he resurfaced in front of her.

"You could've warned me!" She said. "Just…try not to look, okay?" She said, turned around, and dived under. Yuta had to admit he was surprised she didn't seem more upset about him blackmailing her into staying naked, but he wasn't gonna complain. Sure, he may be a pervert, but he was also a teenager.

So the two swam around a bit, with Yuta trying to discreetly check out his sister, getting good views of her ass, her chest, and even her pussy, which he was surprised to see was shaved, but made him feel joyous. She quickly caught on that he was looking at her though, but other than a few glares his way, and a flushed face, she didn't actually say anything, so he continued to enjoy her gorgeous naked body moving around everywhere, especially as she occasionally bumped into him.

At one point though, she accidentally brushed up against his dick, which was still rock hard. They out jumped, with Aoi turning around quickly, causing her breasts to bounce wildly.

"A-ah…" He said, and was about to apologize when he noticed her gaze. Her cheeks were incredibly flushed, and she was panting, more than she usually did.

"Yuta…" She said, and the way she said his name turned him on even more, nearly making him groan. "I…" She crept up close to him, and gently placed her hand on his crotch, directly over his dick.

"A-Aoi!" He exclaimed, then moaned as she started to rub it. He could feel her hot breath on his neck as she pressed her body against his, her breasts soft as they squished against his chest.

"It's so…big…" She said, and he shuddered. "I…I didn't realize how much I liked you…looking at me…" Was she…turned on? "Yuta…I want to…will you do it with me?"

"Yes!" He said with enthusiasm.

So the two left the pool, dried off, giving Yuta even more chances to ogle her, to her delight, and as soon as they were inside, Aoi jumped the boy, and the two fucked, multiple times. They did it on the couch, on the floor, on the table, on their beds. They did it all day until their parents came home. Of course, Yuta thought it would be a one time thing, but when Aoi went into his room that night, it became clear this was a permanent thing.

And he was happy about it.