When Shinichiro returns home unexpectedly, he loses all restraint and makes a move on his mother, Marina. However, Marina, having spent time alone, has already begun satisfying her own desires and harbors a secret passion focused on her anus. Unable to suppress his feelings, Shinichiro confides in his best friend, but ultimately finds himself drawn back to touching Marina's body. Meanwhile, Marina attempts anal sex for the first time, her pristine anal ring stretched wide by an extremely thick cock. Her lewd appearance leaves Shinichiro utterly shocked. Filled with forbidden experiences, this story thrills with an intense interplay of love and desire.