The incident began when koyokata (a section of a local domain which was in charge of dealing with all works related to the central bakufu government and the Imperial seat) of the Minakuchi domain complained about the acts by the Shinsengumi to koyokata of the Aizu domain at the Aizu domain residence.
水口藩公用方が会津藩邸にて会津藩公用方に新選組の所業の悪さを訴えたことに始まる。