He was engaged in consolidating Hakodate/Goryokaku from January to February, and when the news of an attack by the army of the new government reached his ears in March Toshizo participated in Naval Battle of Miyakowan which targeted to seize Azuma-kan of the army of the new government; however, this operation failed, and many died or were wounded, but Toshizo managed to return safely.
1月から2月にかけては箱館・五稜郭の整備にあたり、3月には新政府軍襲来の情報が入ったため、歳三は新政府軍の東艦奪取を目的とした宮古湾海戦に参加、作戦は失敗し多数の死傷者が出るも、歳三は生還する。