Seiichi Osabe is an only child living a mundane life. Just like any middle schooler, he has friends, a crush on a girl, and loving parents. However, Seiichi's mother is extremely overprotective, which causes others to view him as a mama's boy.

Although he doesn't consider her behavior to be unusual, a certain incident starts 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 isn't as normal as he thought.