He successfully had the son of his sister made Crown Prince by taking advantage of the Jowa no Hen (Jowa Conspiracy), and when the Crown Prince became Emperor Montoku, he controlled the Imperial government and attained the position of Daijo-daijin (Grand Minister of State).
承和の変で妹の生んだ皇子を立太子させ、その文徳天皇が即位すると朝政を掌握し、太政大臣に昇った。