Tsundere Inran Shoujo Sukumi

When the main character visits his school during summer holiday, he accidentally finds Sukumi, his classmate, masturbating in female locker room. "If you don't want me to bring it out into the open, come here every day!" Her orders gradually get bolder and they have sex in the pool...? Super erotic summer holiday! His endless summer with Sukumi now starts!
(Source: ErogeShop)