The federal lord of Kofu, Tunatoyo (Tsutomu Isobe), was elected to be the next General. On his way on a trip to Edo for the ceremony, his scapegoat was shot. Oometsuke ordered an Oniwaban, Shinnosuke Takusyoku (Mikijiro Hira) to take Tsunatoyo to Edo safely. However, the enemy turned out to be his younger brother and the federal lord of Tatebayashi Kiyotake (Yoshihiro Kobayashi). On top of that, the Oniwaban sent by Kiyotake to assassinate Tsunatoyo was Shinsuke's father-in-law, Genshin Uno (Shigeru Kamiyuama).
Sorry, but for now we weren't able to find movies like Undercover Ninja: Secret Assassins.