 Tatsumi fought in the Aizu campaign, and led the Kuwana forces even north on Matsudaira Sadaaki's orders to join the Ōuetsu Reppan Dōmei, surrendering in Shōnai Domain (present-day Yamagata Prefecture) some time later.Following the end of the Boshin War, Tatsumi was placed in confinement in January 1871, and changed his given name to Naofumi.However, he was soon pardoned by the new government, and returned to Kuwana Domain as a junior councilor after pleading his loyalty to Emperor Meiji.