Yes, since the film was not released in Japan, Toei wouldn't have had any extant elements. No one would have come to see a Korean-made film in Japan back in those days. Even HK films didn't break the Japanese market until Bruce Lee posthumously became an international superstar with ENTER THE DRAGON.
August Ragone
Author, EIJI TSUBURAYA: MASTER OF MONSTERS
Coming this fall from Chronicle Books

Director, SHOCK IT TO ME! Classic Horror Film Festival
Oct. 5-7, 2007 • Castro Theatre • San Francisco