―A butterfly you met at the 50th side road, passing under the great gate, will you meet a fated person?― That is the "good luck phrase" taught to the protagonist by her grandmother. In the summer of her 17th year the protagonist Yoshino chases a butterfly underneath a great gate, and ends up in a Taisho era red light district "Yoshiwara" where cherry trees are blooming in profusion. There she meets a young writer Harufumi, and an entertainer Kochou. Every night stimulating things repeat at Yoshiwara, and with the two men Yoshino searches for a way to return to her modern era but...