Emperor Seiwa was the 56th emperor of Japan, according to the traditional order of succession. Seiwa's reign spanned the years from 858 through 876. He was the ancestor of the Seiwa Genji, who later became the leaders of the warrior class. Born: May 14, 850 Died: January 11, 881 In office: October 11, 858 – December 22, 876 Wiki link