Because on July 14, 1871 it was decided that each domain in the Satchodohi should supply one Sangi (councilor) to the Sangi cabinet, which effectively had the final say of constitutional matters (according to the order in which they were recommended, the members of the Sangi cabinet were Kogoro KATSURA from Choshu, Takamori SAIGO from Satsuma, Shigenobu OKUMA from Hizen, and Taisuke ITAGAKI from Tosa); thereafter, a majority of the Sangi cabinet was made up of people from the Satchodohi.
1871年（明治4年）7月14日、実質的な最終決済をする参議内閣に薩長土肥一人ずつの参議を供給することとなったため（参議に推された順番で、長州：木戸孝允、薩摩：西郷隆盛、肥前：大隈重信、土佐：板垣退助）、これ以降、薩長土肥出身者が参議の大部分を占めることになった。