According to "Gizankokaku" (a book of desultory gossip stories) by Guken which is said to have come about at the end of the Azuchi-Momoyama period, Koji was born in Echigo Province.
安土桃山時代末期のものとされる愚軒による雑話集『義残後覚』には、筑後国の生まれとある。