After Emperor Kanmu's era, his eldest son, Emperor Heizei succeeded to the throne, his younger brother, Imperial Prince Kamino (later called Emperor Gosaga) became the second successor to the Crown Prince by following the Emperor's will after the Emperor Heizei, who was born weak.
桓武の後は、桓武長子の平城天皇が皇位継承し、その遺志に従う形で病弱であった平城の次にはその弟の神野親王（後の嵯峨天皇）が皇太弟に立った。