Near the end of the Muromachi period, Sasaki Rokkaku of Omi Province, using the castle of Kannonji as a base, started to steadily build up military might. He made light of commands from the Ashikaga shogunate, and eventually began to ignore the shogunate altogether. In 1487, General Ashikaga Yoshihisa brought with him an army to stamp out this rebellion, and a battle between Ashikaga and Rokkaku’s camps ensued.

Ashikaga mobilized daimyo from several provinces in the castle of Kannonji, the headquarters of the Rokkaku; as a result, Rokkaku Masayori and Rokkaku Takayori (Masayori's son) were forced to flee to the castle of Kōka. The factual accuracy of their escape is debated and it is likely that they gave up the town to avoid a direct confrontation instead. Ashikaga then moved his base to Anshiyoji of Kurita District and attacked the castle of Kōka. Kōka fell, but the Rokkaku duo escaped and ordered the Kōka warriors who followed them to mount a heavy resistance against Ashikaga using guerilla warfare. Exploiting their geographical advantage in the mountains, the Kōka warriors launched a wide range of surprise attacks against Ashikaga’s forces, and tormented them by using fire and smoke on Ashikaga’s camp during the night.

The guerilla warfare prevented a final showdown, until Ashikaga died in battle in 1489, ending the three-year conflict and sparing the lives of the Rokkaku duo. The elusive and effective guerilla warfare used by the Kōka warriors became well-known throughout the whole country.

As a result of this victory, the local samurai in the 53 families who participated in this battle were called "the 53 families of Kōka".

This also marked the first time that the ninja of Kōka were drafted as a regular army by their lord. Previously, they were only mercenaries and it was not uncommon to have warriors from Kōka on both sides of a battle.

Any actual lineage of the Kōga-ryū ended with the death of Fujita Seiko on January 14, 1966. In an interview given to the 1963 edition of Bugei Ryuha Daijiten, a record of legitimate martial art schools, Seiko indicated that 'nobody knows this ryu today.' He is often referred to as the "Last Ninja".

Reference:

Online article entitled: Koga Ryu

Wikipedia, free encyclopedia

http://en.wikipedia.org/wiki/Koga-ryu

What we teach:

Our curriculum follows exactly the requirements of the K.R.N.S., thus all ranking comes directly from them. However, we do borrow many techniques from various Iga based Ninja schools, Historic scrolls, and modern combat Ninja schools, to create a rather well rounded Ninja training.

The techniques revolve primarily around the use of body mechanics (Tai-jutsu) and mindful intention training, with a wide array of weapons. Usually each weapons is the focus for a particular rank in training. Some of the weapons taught include:

Yawara, Hanbo, Tanto, Wakizashi/Kodachi, Katana/Daito, Ninja Bikento, Shuriken, Jutte, Shuko, Ashiko, Jo, Bo, Yari, Naginata, Gusari Fundo, Manriki Gusari, Hojo, Kama, Kyoketsu Shoge. 

Koga Ryu Ninjutsu is the most weapons intensive system that we teach. **Please note that the weapon's techniques taught as part of the Yoshin Ryu Jujitsu curriculum are not the same as those taught in the Koga Ryu Ninjutsu curriculum.

There do exist several unique unarmed methods of fighting that are also taught at each rank level, making the system more adaptable. Particular "Ninja Mindset" training is also taught at each rank level, allowing practitioners to apply these skills in their lives.

The following are clips of Jinichi Kawakami Soke performing several Koga/Koka Ryu Ninjutsu techniques.