Tonari ni Sumu Oshiego to Kekkon Shitai no desuga, Doushitara OK ga Morae Masu ka?

A high school student starts living independently and is suddenly proposed to by his teacher, Ms. Mitsuki. Though her appearance changes, he suspects she may also be the woman he has a crush on who lives next door. Despite the age difference, they begin a tentative relationship. She frequently enters his apartment and flirts with him at school, nearly exposing their relationship to his classmates. The story follows their comedic interactions as they navigate this unusual dynamic.