It is believed that Gyokushin Ryu’s founder Sasaki Goemon was originally from the Gyokko Ryu or that the techniques of the Gyokushin Ryu were based on the Gyokko Ryu.
It is not known in the west as to what the fighting techniques of the Gyokushin Ryu are. All that is really known is that it uses sutemi throws. What is known is that this school concentrated more on the espionage side of ninjutsu, rather than the fighting side. It has been said that the specialties of this ryu were the kusari fundo, ninjutsu, koppojutsu, jutaijutsu, kenjutsu and iaijutsu, although we have no confirmation on this.
Hatsumi says this about the Gyokushin Ryu in his book Hiden Ninja Submission:
GYOKUSHIN RYU NINPO “It is a faction of kosshijutsu and was founded by Sasaki Orouemon Akiyari. A characteristic of the ryu is found in the kind of weapons it uses. Gyokushin Ryu is known for its superior use of nagenawa, a lasso.”