Constantly being at the mercy of local bullies who view him as nothing more than a servant, Masahiro Setagawa is defenseless and feels as though he has no hope of finding a way out of his cycle of abuse. That is, until his life is forever changed when he meets Kousuke Ooshiba- known as the "Bear Killer" for his ability to take down gangs in the neighborhood. Fast forward a year, and Masahiro and his former friend Kensuke Ooshiba find themselves attending the same high school, with Kousuke as their new math teacher. As Masahiro comes to view Kousuke as his "hero" and Kousuke feels an intense desire to protect him, their normal lives soon take a dramatic twist- Kensuke's childhood friend Asaya Hasekura returns, and begins to see Kensuke as more than just a friend, taking him by surprise. Facing societal taboo, the three boys must overcome their differences and pursue forbidden love, or risk being separated forever.