The temple was named 'Kosho-ji' (興正寺) after 'Koryu Shobo' (興隆正法, lit. Spreading the noble and correct Dharma) of Emperer Juntoku's order, which was associated with Prince Shotoku, and operated as a center for the dissemination of Shinshu sect nenbutsu.
順徳天皇から聖徳太子にまつわる「興隆正法」の勅願を賜り、これより寺号を「興正寺」とし真宗念仏宣布の根本法城とした。