In the past, Izumo saved a youngster named Ryuta from a brutal youkai. He promised to reunite with Ryuta and go on adventures together, but he left without keeping his word. Fate intervened, and Ryuta and Izumo encountered each other again, although Izumo professed to not remember their agreement or knowing Ryuta. Nonetheless, Ryuta remained loyal to his friend and diligently prepared for their upcoming exploits. Undaunted, Ryuta embarks on a quest with Izumo!