It was founded in March 1891, added new members such as the peerage and large taxpaying members of Diet as well as original members, incumbent members of the House of Peers to the Doshi-kai that had been founded in November 4, 1890, making out the voluntary document and rules stipulating that it should hold assemblies on every Monday, Wednesday and Friday (the name of the group 'Sanyo' [Three-day-a-week] derived from that).
1890年11月4日に発足していた同志会が、翌年3月に新たに従来の現職貴族院議員以外の華族や多額納税議員をも会員に加え、毎週月・水・金曜日に会合を開く（会派名の「三曜」はこれに由来する）こととする主意書・規約書を作成して発足した。