Fukano, an elderly novelist who grew up in the mountains of Tokyo, met a young woman, Kana, for the first time in Fukagawa. Overcoming the age difference, they are strongly attracted to each other. However, in Fukano, in addition to the problem of downtown and uptown, there was a deep “river” that separated women and men. However, Kana, on the other hand, easily crossed that "river" due to her sexual love with Fukano. "I never thought I'd live west of the Sumida River," Kana said. However, behind this lies the conspiracy of Fukano's old lover, Junko. The two get married, but Kana's behavior is gradually haunted by a mystery, and the shadow of her detective and old man flickers. The core of the mystery involved a strange sex shop