In January 1868, he took part in the Battle of Toba and Fushimi, and he allegedly died in battle in Yodo Domain (according to Jingoro YOKOKURA) or died on the battleship 'Fujiyama' while withdrawing to Edo (according to entry in "the list of war dead of the Eastern Camp in the Boshin War" in Gokomiya-jinja Shrine, where the name is written with a different kanji for Yu).
慶応4年1月、鳥羽・伏見の戦いに参戦、淀藩にて討ち死に（横倉甚五郎）、または江戸引き上げの軍艦「富士山(軍艦)」船中にて死亡（御香宮神社『戊辰東軍戦死者霊名簿』、今井勇次郎として記載）とされる。