Satou Kakeru has long accepted that his past life’s memories of being a Hero in a fantasy world has no place in the current modern society. Until one day, the Demon King – Suzuki Teru – transfers into his school and throws Kakeru’s normal life out of its axis. An incident leads to their separation and three years later, Kakeru’s big brother drops a bomb on him. “They say the key to reviving the Demon King is in the academy island.”