At the age of 15, Saito went back to the other world, where he became the Great Sage and defeated the Demon Lord.Saitou returns to Japan with the Great Sage's power shortly after the door between the other world and the real world opens.In reality, however, 19 years have passed.Saito, who had been far away for a long time, met Kanako, his childhood friend who is now a single parent.However, it appears that someone is pursuing Kanako's life... The story of a slow-living wannabe Great Sage who returned from another world begins!