Boku ni Sexfriend ga Dekita Riyuu

This is an anime adaptation of the Doujinshi of Ailail.

Due to family circumstances, our protagonist moves into a building located on the outskirts of Tokyo. However, he quickly fell in love with his neighbor, Hitomi Rimuro, and takes as a bad habit to spy on her when she changes. One day, she discovers it and proposes that they become sexual partners.