Teacher, I'm Already Grown Up / Uhou Renka

Adaptation of the hentai game of the same name by studio "Caramel Box". Ryohei returns to his hometown after a long absence. He meets a girl named Karen, who is the mascot of a local tenement house. Her charming curves drive our hero crazy, but then his ex-girlfriend Nagisa appears, who knows Ryo even better than he knows himself.