On July 15, 645, immediately after Isshi-no-hen, Emperor Kogyoku stepped down from the throne, tried to pass over the throne to Naka no Oe no Oji but as a result of a meeting between Naka no Oe and Kamatari, the younger brother of the Emperor, Prince Karu, acceded to the throne and became Emperor Kotoku, with Naka no Oe no Oji becoming the Crown Prince.
皇極4年（645年）6月14日、乙巳の変の直後、皇極天皇は退位し、中大兄皇子に皇位を譲ろうとしたが、中大兄と鎌足との相談の結果、皇弟・軽皇子が即位し、孝徳天皇となり、中大兄皇子が皇太子になった。