Imperial Prince Tsunesada, son of Emperor Junna, was named Crown Prince for Emperor Ninmyo, but was disinherited at the time of the Jowa Incident that occurred immediately after the death of the retired Emperor Saga in 842, and Imperial Prince Michiyasu was named Crown Prince.
仁明天皇の東宮には淳和上皇の皇子恒貞親王が立てられていたが、承和9年（842年）の嵯峨上皇の崩御直後に起きた承和の変で恒貞親王が廃され、道康親王が立太子される。