Seiwa

…the throne as the emperor Seiwa at the age of nine. Yoshifusa, thereupon, had himself appointed regent—the first instance in Japanese history of a person not of royal blood being named to this position. This led to the practice of the Fujiwara persuading emperors to retire at a comparatively early…

…mid-9th century, however, when nine-year-old Seiwa ascended the throne, his maternal grandfather, Fujiwara Yoshifusa, created the office of sesshō, based on the post once held by imperial family members such as the empress Jingū and the princes Nakano Ōe and Shōtoku. Yoshifusa’s son Mototsune became sesshō during the minority of…