ご存知！旗本退屈男Ⅴ 甲府城に渦巻く暗雲！

Sawatari Shusui saved Princess Hiroko of the Konoe family, who was about to be married to Tokugawa Tsunatoyo. However, Hiroko, a tomboy, disappears. As someone is after Hiroko's life, Shusui pursues her whereabouts... Meanwhile, Sasao Yoshinari and Shusui's sister, Kikuji, who were following Shusui, meet a young man and Kikuji is captivated by him, but they do not realize that he is Hiroko in disguise as a young man. Shusui is set to search for Hiroko with her attendant Orui, but that night they are attacked by a group of ninjas at their inn.