According to Nisshu Shonai Gunki, there is an entry stating that Mitsunari ISHIDA or Ieyasu TOKUGAWA told Tadatsune, who had returned from Korea after the death of Hideyoshi TOYOTOMI, that Tadamune IJUIN was thinking of rebellion, but there is no other historical evidence of the same era to prove it.
豊臣秀吉の死後、朝鮮から帰国した忠恒に石田三成もしくは徳川家康が伊集院忠棟に叛意があることを伝えたという日州庄内軍記の記述があるが、それを裏付ける同時代史料はない。