Emperor Kōkō Japanese emperors 2019.09.04 2019.07.05 The 58th Emperor of Japan. Emperor Kōkō inherits the Y gene The period of reign 884 – 887 Another name 光孝天皇(Emperor Kōkō) 時康(Tokiyasu)仁和帝(Ninnanomikado)小松帝(Komatsunomikado) Mausoleum of Emperor Kōkō