When Hideyoshi TOYOTOMI died in 1598 and Ieyasu TOKUGAWA began to exert his power, Sakon considered it dangerous, and proposed a plan to assassinate Ieyasu to Mitsunari, but Mitsunari considered it unjustifiable and did not accept it.
慶長3年（1598年）、豊臣秀吉が没して、徳川家康が権力を振りかざすようになると、それを危険に感じた左近は三成に家康暗殺計画を持ちかけるが、大義名分にこだわる三成はそれを受け入れなかった。