Initially, a prince of Emperor Junna, Prince Tsunesada, was recommended to become the crown prince; however, after the Showa Incident (842) Prince Tsunesada was dethroned, so instead Emperor Nimmyo's first prince, Michiyasu, became the crown prince.
当初、淳和天皇の皇子恒貞親王を皇太子に立てたが、承和9年（842年）の承和の変により、恒貞は廃せられ、代わりに仁明天皇の第一皇子道康親王が立太子した。