It is believed that the techniques of Gyokushin Ryu are based on Gyokko Ryu. In the west, not much is known of the combat techniques of Gyokushin Ryu, except that it may have utilized many sacrifice-throws. The school specialized in the espionage aspect of Ninjutsu. This school was kept secret and unmixed with other schools until it passed to Toda Nobutsuna (1624-1644).