Kà Âga-ryà « (ç²è³ÂæµÂ, "School of Kà Âga") is an umbrella term for a set of traditions of ninjutsu that originated from the region of Kà Âga (now the city Kà Âka in Shiga Prefecture). The samurai of Kà Âga-ryà « were known as "Kà Âga-no-mono", and operated as shinobi throughout Japan's turbulent Sengoku period.
The beginnings of the Kà Âga-ryà « may be traced to near the end of the Muromachi period. While the district of Kà Âga, in à Âmi Province, was under the jurisdiction of the Rokkaku clan, it was a kind of autonomous municipality, composed of localized unions called sà  (). The Kà Âka confederacy called itself the Kà Âka-gun Chà «sà  (ç²è³Âé¡ä¸Âæ£, "General Assembly of Kà Âka District"). All important decisions in the municipality were made by a majority vote from the union representatives. This kind of system was uncommon for the period in question.
At this time, the leaders of the Rokkaku clan, using Kannonji Castle as a base, started to steadily build up military might. They gave little weight to 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 the Rokkaku forces ensued. Ashikaga mobilized daimyà Âs from several provinces against the castle of Kannonji, the seat of the Rokkaku; as a result, Rokkaku Masayori and his son Rokkaku Takayori were forced to flee to the castle of Kà Âga. The factual accuracy of their escape is debated; 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 KÃ Âga. KÃ Âga fell, but the Rokkaku duo escaped again and ordered the KÃ Âga samurai who followed them to mount a heavy resistance against Ashikaga using guerrilla warfare. Exploiting their geographical advantage in the mountains, the KÃ Âga 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 guerrilla warfare prevented a final showdown, until Ashikaga died in battle in 1489, ending the three-year conflict and sparing the lives of the Rokkaku.
The elusive and effective guerrilla warfare used by the KÃ Âga samurai 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 KÃ Âga".
The last reported Sà Âke of Kà Âga-ryà « was 14th headmaster Fujita Seiko (1898âÂÂ1966). In his autobiography Doronron: Saigo no Ninja ( "The last ninja", October 1958), Fujita categorically stated that he had not and would not teach anyone ninjutsu, and would not pass on the school.
The Bugei Ryuha Daijiten, a definitive Encyclopedia of martial arts schools, catalog of Koryà « Bujutsu (old schools) and Gendai Budà  (new schools) of Japanese martial arts (budà Â) states that no one knows the teachings of this school today. Few today who state a connection to Koga Ryu can show any evidence to refute this claim, and it is in all likelihood that there are no authentic living traditions practiced today.