Ose Koichi was born 27th October 1937 in Yokohama. His real name is Ose Kazunari.

He graduated from Keio University School of Foreign Languages. In 1952 he entered the Daiei film company (they made Rashomon among other films) and appeared in a number of films. In 1958 he starred in the TV series Gekko kamen where he gained tremendous popularity with children as the mysterious masked hero.