The Emperor Komei, who got furious about the bakufu which signed the Treaty of amity and commerce between the United states and Japan by ignoring the Emperor's intention, joined the plan of the Mito Domain, which was trying to regain power in the shogunate government.
日米修好通商条約許さずの天意を無視する形で条約調印に踏み切った幕府に激怒した孝明天皇は、幕政における復権を画策していた水戸藩の朝廷工作に乗った。