Japan is full of unassuming signs marking the sites of historical significance of varying degrees, from a samurai lord’s residence to a long-defunct elementary school, to the birthplace of some local delicacy. In the historic Tokyo downtown of Sumida City, there is a series of historical markers called Onihei Jokei, dedicated to fictional events that took place on the spot. Onihei Hankachō was a popular jidaigeki novel series written by famed author Shotaro Ikenami and serialized from 1967 to 1989. It has been adapted into other forms of media numerous times, including…