Koshiro MAGAKI (Ryunosuke KAMIKI) is the son of a salmon dealer for the Nibuyama Domain of Echigo. His saintly nature doesn’t make him the best businessman, but he lives a peaceful life surrounded by people who care for him dearly. But one day, a group of officials rush to his home, and his father Sakubei reveals shocking news to him: He is actually Koshiro MATSUDAIRA, descendant of the shogun TOKUGAWA Ieyasu and heir to the Nibuyama Domain! Koshiro also learns that his real father, Ikkosai (Koichi SATO), has left the estate to him and retired. This Cinderella story of a commoner becoming a lord overnight seems like great fortune, but it turns out that the Nibuyama Domain is actually in debt for 10 billion yen! As Koshiro remains at a loss for what to do, Ikkosai says that Koshiro simply has to declare the domain’s bankruptcy on the debt’s due date and everyone will be saved. However, Ikkosai’s actual plan is to have his son shoulder all the responsibility and make him commit hara-kiri! Koshiro is faced with the decision of a lifetime: pay back 10 billion yen or kill himself! What will this young prince do in the face of his life’s biggest crisis?!