On July 27 of the same year, the pact between Satsuma and Tosa was expanded to include Aki, which was a neighboring domain of Choshu, further strengthening ties among major clans.
この薩土盟約は、更なる雄藩連合推進のため、同年6月26日、長州藩の隣の安芸藩を加えた薩土芸三藩約定書に拡大発展する。