Gobaku: Moe Mama Tsurezure

Haruka Miyama sees Hiro, her best friend's son, as a member of her family. However, things become complicated when Hiro confesses his love and seduces Haruka while the latter's husband is on a business trip. Knowing that what they are doing is wrong, Haruka tries as best she can to reject him without hurting him, but she ends up giving in.