On January, 13th, 4th year of Keio, Boshin War started with the Battle of Toba Fushimi; in place of Isami KONDO, who was wounded in Sumizome Incident, Toshizo lead Shinsen-gumi and fought as a deputy of commander but was defeated against the army of the new government in gun fighting.
慶応4年1月3日鳥羽・伏見の戦いに始まる戊辰戦争が勃発し、歳三は墨染事件で負傷した局長近藤勇の代わりに新選組を率いて戦うが、新政府軍の銃撃戦の前に敗北する。