Masahiro Setagawa is a despondent adolescent who is frequently exploited as an errand boy by the local bullies. Masahiro, who is defenseless, understands that no one will ever save him. His life is turned upside down when he encounters Kousuke Ooshiba, a guy known as the "Bear Killer" who takes out local gangs. Masahiro and his old buddy, Kensuke Ooshiba, start high school a year later, only to discover that Kousuke is their math instructor. As the three become closer, Masahiro begins to see Kousuke as his "hero," and Kousuke develops a strong desire to protect Masahiro. However, their usual lives are turned upside down when Kensuke's childhood buddy, Asaya Hasekura, arrives, surprised to find Kensuke as more than just a friend. Will the three lads be successful?