Gyokko Ryu Koshijutsu is the oldest of the nine martial art traditions that make up the Bujinkan System, and it is safe to say that it is the core style of the majority of our arts. Hatsumi Sensei has stated that the koshijutsu forms the basis of the following systems: Togakure, Koto, Gikan, Shinden Fudo, Gyokushin, and Kumogakure. The name 'Gyokko' means Jeweled Tiger, or Tiger Jewel, and may refer to the eye of the tiger.
The method of movement and basic principles were developed in China during the Tang Dynasty (618-907 AD). It is thought to be developed by either a smaller man or a woman, based on the movement. It is known that there was a woman in the court of Chanan (the capital of the Tang Dynasty) very well known for her martial arts abilities. When the Tang Dynasty fell in 907, many of the Chinese nobility escaped into Japan. The names Yo Gyokko (Yao Yu Hu) and Cho Gyokko are associated with the art leaving China and arriving in Japan. (They possibly were the same person). General Ikai (or Ibou) is also associated with the origin of Gyokko Ryu. According to Hatsumi Sensei that person could also be somebody (bou) from foreign (I) country.
The first actual Soke of what we would call 'official Gyokko Ryu' was Tozawa Hakuunsai. His name suggests a connection with Hakuun Ryu Ninjutsu, which no longer exists. This was in the Hogen Era (1156-1159), which makes Gyokko Ryu one of the oldest documented martial art systems in Japan. Hatsumi Sensei has said in fact that koshijutsu is the basis of martial arts in Japan, and that it forms the backbone (koshi) of the fighting systems in the Iga Region (I'm assuming he's referring to all ninjutsu clans). The Bugei Ryu-ha Daijiten refers to the Gyokko Ryu as "Kosshijutsu, Shitojutsu, Ninpo".
Koshijutsu means 'to knock down an enemy with one finger'. Therefore, intense striking training was involved, mostly to the fingers, toes and knuckles, but also with all parts of the body. The style is characterized by powerful blocks with the knuckles that destroy the muscles of the opponent, ripping, piercing and tearing techniques with the fingers and toes, powerful stomping kicks, and close grappling with locks and throws. It was taught in the Gyokko Ryu to only use as much strength as needed to defeat the opponent. They were also known for their skill with the sword, 6-foot staff and knife.
THE NINE RULES OF THE GYOKKO RYU:
The character NIN means to guard the nation with even your life.
Forget self; be patient and do not fear dying.
In danger, say and show nothing.
As a strong enemy comes, keep an indomitable spirit.
Serve and protect the master, as you must your parents.
Vices dissipate your proficiency.
Being drunk affects your judgement.
Destroy the enemy?s power but leave his life.
Do not teach others without the master's permission.
Headmasters of Gyokko Ryu
Suzuki, Saburo Shigeyoshi
Suzuki, Kojiro Mitsu
Tozawa, Nyudo Geneai
Kato, Ryu Hakuun
Sakagami, Goro Katsushige
Sakagami, Taro Kunishige
Sakagami, Kotaro Masahide
Sougyoko, Kan Ritsushi
Toda, Sakyo Ishinsai
Momochi, Sandayu 1
Momochi, Sandayu 2
Momochi, Tanba Yasumitsu
Momochi, Taro Saemon
Toda, Seiryu Nobutsuna
Toda, Fudo Nobuchika
Toda, Kangoro Nobuyasu
Toda, Eisaburo Nobumasa
Toda, Shinbei Masachika
Toda, Shingoro Masayoshi
Toda, Daigoro Chikashige
Toda, Daisaburo Chikashige
Toda, Shinryuken Masamitsu