Yukiya Ayase is a kind, mild, and innocent university student. His sole remaining family, his cousin Tetsuo, betrays Ayase by auctioning him off to the highest bidder in the hopes of collecting a large enough sum to pay off his debts. Somuku Kanou, a bad-tempered (but extremely wealthy) loan shark, comes to Ayase's aid and purchases Ayase for an amazing 1.2 billion. Kanou appears to recognize Ayase from something that happened between them in the past, but Ayase has no memory of Kanou and has no idea why he "saved" him. Kanou, wanting to keep Ayase close to him, asks that the loan be returned in full and provides the ideal method to do so: by selling his house.