Since Imawaka's father Yoshitomo was defeated and died in the Heiji War when he was at an early age of 7 in 1159, he was forced to enter the priesthood at Daigo-ji Temple and named himself Ryucho (隆超) (or Ryuki (隆起)), then Zenjo after a short while.
今若が7歳の平治元年（1159年）、平治の乱で父義朝が敗死したため幼くして醍醐寺にて出家させられ、隆超（または隆起）と名乗り、ほどなく全成と改名。