Hayate Ayasaki is an unlucky teenager who has worked since childhood to make ends meet due to his parents' irresponsible behavior. One day on Christmas Eve, he finds out that his parents shoulder him with a massive ¥156,804,000 gambling debt, the Yakuza (who the money was borrowed from in the first place) plan to settle that debt by selling his organs on the black market. While running away from the debt collectors he ends up meeting Nagi Sanzenin, a young girl who is the sole heir of the wealthy Sanzenin estate, and due to a misunderstanding, Nagi ends up falling in love with Hayate. After he rescues Nagi from some kidnappers, she hires Hayate as her new butler.