During the most horrible Shoka Famine, he became Crown Prince when he was just ten years old in August 1258, then he succeeded to the throne in the following year after his brother, Emperor Gofukakusa passed the throne to him.
正嘉2年（1258年）8月、惨烈を極めた正嘉の飢饉の最中、10歳で立太子、翌正元元年兄の後深草天皇の譲りを受けて践祚。