The rule of Shogun Ashikaga Yoshimochi witnessed a significant diplomatic crisis in the fifteenth century following the invasion of Tsushima by forces from Joseon Korea and the breaking-off of diplomatic relations with Ming China. The shogun renounced the title "King of Japan," bestowed upon his predecessor by the Ming emperor, and used shinkoku rhetoric in official correspondence with the continent. This article reveals the reasons for Yoshimochi's stance, concealed within the ceremonial and ritual aspects of his rule. First, it investigates diplomatic relations between the Ashikaga Shogunate and the Ming government, and shows how the domestic political agenda and ceremonial cycle of the Japanese imperial court influenced shogunal decisions regarding the reception of diplomatic envoys. Second, it argues that Yoshimochi's termination of diplomatic exchange with the Ming was a political reaction to the reports of divine intervention brought by the priests of the Hachiman bodhisattva syncretic cult, rather than a geopolitical measure responding to the Joseon invasion of Tsushima. The article refutes the notion that the shogun demonstrated hostility towards foreigners caused by emerging national awareness. Finally, examining visits of Korean envoys after the diplomatic crisis of 1419, this article outlines the transformation of diplomatic protocol from Ming-dominated tributary ceremonies to a framework of Buddhist cultural exchange.