セクシーな大人の女性以外興味のないボク。そんなボクの妹は体型も幼くガキ臭くてまったく性的対象にならない。なのにやたらとボクにベタベタしてくるから正直少しうざい。そんな妹がボクと一緒にお風呂に入る！と言い出した。まぁ間違ってもガキに欲情なんてしないと思っていた…。しかし実際に妹の裸を見たら…ヤバい！意外とエロい体に成長している！ムクムク大きくなるボクの股間！そして悪ノリした妹がおっぱいを押し付けてきて…理性崩壊！うっかり手を出してしまった！すると妹は体だけではなく中身も立派なドスケベ女性で、濃厚なセックスに発展！お風呂だけでは満足できず…。
I'm only interested in sexy, mature women. My little sister, however, has a ish figure and is completely unattractive to me sexually. Yet she's always clinging to me, which is honestly a little annoying. Then she suddenly said she wanted to take a bath with me! I thought there was no way I'd get aroused by a ***… But when I actually saw my sister naked… Damn! She's grown into a surprisingly sexy body! My crotch started to swell! Then my sister, getting carried away, pressed her breasts against me… I lost all self-control! I accidentally reached out and touched her! It turned out my sister was not only physically but also a full-fledged pervert inside, and it escalated into intense sex! A bath wasn't enough to satisfy me…

– JavGG.net