Wikipedia
Kōga-ryū
Kōga-ryū (甲賀流, "School of Kōga"; occasionally transliterated as "Kōka") is an ancient school of ninjutsu, according to Japanese legend. It originated from the region of Kōga (modern Kōka City in Shiga Prefecture). Members of the Koga school of shinobi ( ninja) are trained in disguise, escape, concealment, explosives, medicines and poison; moreover, they are experts in techniques of unarmed combat ( Taijutsu) and in the use of various weapons.