The Ko brothers were killed together with other family members by Yoshinori UESUGI (foster son of Shigeyoshi who was killed by Moronao) of the Tadayoshi group at Mukogawa River (Itami City, Hyogo Prefecture) in Settsu when they were on their way from Settsu to Kyoto under guard.
高兄弟は摂津から京都への護送中に、待ち受けていた直義派の上杉能憲（師直に殺害された重能の養子）により、摂津の武庫川（兵庫県伊丹市）で一族とともに謀殺される。