Seiichi Osabe is an only child leading a mundane existence. Like any typical middle schooler, he has friends, a crush on a girl, and loving parents. However, Seiichi's mother is extremely overprotective, which leads others to view him as a mama's boy. Although he does not consider her behavior to be unusual, a certain incident begins to open his eyes to just how dangerous her affection is. As Seiichi tries to break free from her grasp, he learns that his life is not as normal as he thought.