In 851, when he underwent the ceremony of attaining manhood at Togun-den, he was treated very kindly, as the Emperor Montoku himself had placed the court headgear on Mototsune's head, and he was also promoted to the court rank of Shorokuijo (Senior Sixth Rank, Upper Grade).
仁寿元年（852年）東宮殿で元服した際に、文徳天皇が自ら加冠するほどの厚遇を受け、正六位上に叙される。