The characters Oko and Seiji, a clever man who is known to solve mysteries, run a lending shop in Edo, one of the largest cities iin the world under the Tokugaya, renting out old items.
Oko and Seiji own and run the Izumo-ya lending shop in the Fukagawa district of Edo. Several of the items they lend are old and have become tsukumogami. Seiji is clever and, with the help of the tsukumogami, has a reputation for being able to solve mysteries and other difficult problems. Edo grew to become one of the largest cities in the world under the Tokugawa. 
