The main character, Yuuichi, is a boy who loves his stepmother, Misako. However, it was a typical mother-son relationship until he learned about the "Mama Club". A secret club at the school that matches boys interested in sex with mothers with incestuous desires. Together, they seek out and enjoy pseudo-incest, that is "mama club"... Yuuichi accidentally discovers this secret is blackmailed into becoming a member and pressured into having sex with the mothers. Unable to resist the pleasure, he spends his days having sex with an unspecified number of "mama's". This causes a change in Yuuichi's love for his mother, Misako. What he truly seeks while drowning in pleasure is his stepmother. On the other hand, what are Misako's feelings for Yuuichi...?