In February 1863, when Kokuji yoriudo was newly established in the court, he was added to this group at the age of 19, but he secretly escaped Kyoto, and joined the Choshu clan, turned down his official court rank and changed his name to Shunsai (Shusai) MORI.
文久3年（1863年）2月、朝廷に国事寄人が新設されると19歳でこれに加えられたが、ひそかに京都を脱して長州藩に身を投じ、官位を返上して森俊斎（秀斎）と改名。