Bored Hatamoto: The Imposter.

Around the Genroku era, there was a man named Saotome Shusui-no-Suke, nephew to the senior councilor Matsudaira Sakon Shogen. He was commonly known as the Bored Samurai of the Hatamoto rank. Just as he was engulfed in boredom, Tokugawa Jo-Kaibo, claiming to be the Shogun's illegitimate child, made a grand entrance into Edo. At the behest of Sakon Shogen, Shusui-no-Suke was tasked to investigate Jo-Kaibo's background and had his young page Kyoya disguise as a woman to infiltrate Jo-Kaibo's gun mansion.