In the Kei-En era, bureaucrats and military typified by Katsura and a leading political party Rikken seiyukai typified by Saionji built a collaborative system called 'emotional agreement' and they alternately served as the prime minister (In the meantime, there was a move to field Masayoshi MATSUKATA, Gonbei YAMAMOTO and Tosuke HIRATA as prime minister, but none of them had stronger foundations of administration than those of the two, so they were forced to give up).
桂園時代は、桂に代表される官僚・軍部と西園寺に代表される有力政党である立憲政友会が「情意投合」と呼ばれる連携体制を組んで交互に内閣総理大臣に就任した（この間にも松方正義や山本権兵衛、平田東助などを首相に擁する動きはあったものの、両者以上の政権基盤を持たずにいずれも断念に追い込まれている）。