Those who support the assassination theory suspect that Yoshimitsu was poisoned by the Imperial Court, who wanted to prevent his usurpation (IZAWA deduces in his novel that the assassin was Zeami).
また暗殺説を取る各氏は、簒奪を阻止しようとした朝廷側による毒殺であると疑っている（井沢は著作で犯人を世阿弥と推理）。