Mujikaku na Osananajimi to Kyoumi Honi de Yatte Mitara The Animation

Hiroki and Meiko are childhood neighbors and classmates. At school Meiko seems like a serious honors student, but at home she casually lounges around his room in revealing clothes, unaware of the effect she has on him. When she catches him staring at her chest, she curiously offers to let him touch her, and their experiment quickly escalates into more intimate acts. Though Meiko remains mostly detached and suggests treating it as practice for a future relationship, Hiroki becomes increasingly overwhelmed. The two agree their old friendship can’t go back to how it was and continue deeper into sexual experimentation.