Nemuru Usagi

A high school student named Kouichi allows a girl he likes to use his address for a gay advertisement, not realizing the consequences. A response arrives, and Kouichi is shocked to find it's from a man he once mocked. To his surprise, the man, Hirokazu, is his teacher. Despite Kouichi's initial intentions, he finds Hirokazu to be kind and lonely, making it hard for him to be cruel. Their interactions grow, leading to multiple dates and Kouichi developing genuine feelings. However, a complication arises because Hirokazu is unaware that Kouichi is one of his students.