The Three Fist Demons or "Three Kenma" are the original three founders of Rinjuken Akugata and major antagonists in Juken Sentai Gekiranger.
4000 years ago, the Three Fist Demons were originally three of the ten disciples of the martial arts and Juuken master Brusa E. However, after an encounter with Long, Maku became inspired to twist Brusa E's teachings and showed Kata and Rageku what he had learned.
The Three Fist Demons then murdered their old master and founded the Rinjuken Akugata martial arts dojo, becoming its first masters. The Rinjuken Akugata dojo recruiting mass amounts of members from across Japan with their sights on dominating the world. In response, the remaining seven disciples of Brusa E founded the GekiJuuken martial arts dojo to combat Rinjuken Akugata's rise, leading to a massive conflict which came to be known as the GekiRin Rebellion. The war between the two dojos ended when the Three Fist Demons were defeated and had their spirits sealed away by the seven Fist Sages of GekiRin.
However, in the modern day, Rinjuken Akugata was revived by Rio, a former disciple of GekiJuken, who unsealed the Three Fist Demons with the hopes of learning from them. While Kata and Rageku happily passed their teachings down to Rio, desiring for him to succeed them as the master of Rinjuken Akugata, Maku instead took back power from Rio after being unsealed.
The Three Fist Demons were later all destroyed by the Gekirangers. After their deaths, Rio became the master of Rinjuken Akugata once again, though he quickly discarded it in favor of the Genjuken style.