Customers of the Hinokiya Drapery Store pay when they make their purchases, as opposed to the normal practice of settling their bills once a year. In return, they receive a 20 percent discount. This system is an example of the astuteness which has allowed the shop's owner, Matsui, to become one of the foremost merchants of the realm. Years before, Matsui renounced his status as a samurai and let go of his stewardship of the Shogun's rural estate in the Kanto district. Instead, he opened a sake distillery, changing his name from Minoru to Matsui in the process.

By the time the novel begins, he has amassed a fortune from the proceeds of his interest in the national shipping firm and his ownership of rice plantations. His money-changing business is amongst the foremost in the country. Most importantly, he has become the banker and financial adviser of the Shogun Tokugawa. He has also acquired the Shogun's protection and gained considerable prestige in the bargain.

Due to Matsui's prominence, Sano, the detective protagonist of the story, is wary of approaching the merchant. However, he has linked the gruesome decapitations (or bundori) of the title to the descendants of General Fujiwara, who lived one hundred years prior to the events of the book. Matsui is one of these. Matsui leads Sano to his imposing house and reveals a shrine to the general. On leaving the merchant, the detective is overwhelmed by frustration; Matsui could very well be the killer, but he has no real evidence to link him to the crimes.