Emperor Seiwa Japanese emperors 2019.09.04 2019.07.05 The 56th Emperor of Japan. Emperor Seiwa inherits the Y gene The period of reign 858 – 876 Another name 清和天皇(Emperor Seiwa) 惟仁(Korehito)水尾帝(Mizunoonomikado)貞観帝 Mausoleum of Emperor Seiwa