A warrior of the mid-Heian period, a great-great-grandson of Emperor Kanmu and a powerful chieftain of the Kantō region. He built his power base in the Bandō area. In 939, he seized successive provincial headquarters in Hitachi, Shimotsuke, and Kōzuke (the Jōhei-Tengyō Rebellion) and proclaimed himself "New Emperor," declaring an independent regime in the east. The court was stunned and dispatched Fujiwara no Hidesato and Taira no Sadamori to suppress him. He was killed in battle in 940 near Sarushima in Shimotsuke Province (present-day Bandō City, Ibaraki), and his severed head was sent to the capital. Though the rebellion was short-lived, it stands as a defining historical event symbolizing the rise of eastern warrior bands and the limits of court authority in the provinces. His burial mound remains in Ōtemachi, Tokyo, revered as a powerful spiritual site.