Due to the attack from the unidentified life forms, Tousuien City was flooded with blood of the victims. The tragedy is called Tousuien Incident, and among the survivors is a student named Senba Shinkurou. Shinkurou lost both his parents from the incidents, so he carried the loss with him when he grew up alone. One day, Shinkurou encountered the same monster from Tousuien Incident. Facing each other, Shinkurou was outmatched and fell into a dangerous situation. In that moment, a beautiful female knight appeared and saved him.