Set in the 1860s, the chaotic final days of the Tokugawa shogunate, Why Not? follows an assortment of proletariats – a peasant farmer just back from the US, his prostitute wife, an Okinawan seeking revenge, an ex-samurai, and an underworld boss – all swept up in the riots that plunged Japan into the 20th century. The film's title refers to the carnivalesque frenzy of the underclass and their apathy towards the future, which would be exploited by the forces of modernization and Meiji imperial control.