The Genjuken (幻獸拳) or "Mythical Beast-Fist" is a practice of martial arts involving the use of powers of mythical beasts as opposed to natural ones and the main antagonists of the second half of Juken Sentai Gekiranger. The Genjuken style is based upon use of a golden type of qi called "Genki" and believes in channeling the power of mythical beasts to ascend past ordinary beasts. It was originally set up by Long with assistance from Rio, the young master of Rinjuken Akugata, and is later revealed to be a front for Long to find a human strong enough to undergo the "Infinite Path" and destroy the world.
After the Three Fist Demons were disposed off and Rio solidified himself as master of the Rinjuken Akugata, Long presented himself to Rio and offered him a chance to master the Genjuken style. Rio accepted and Long conducted the Blood-Oath Ceremony to grant both him and Mele new Genjuken forms. However, Long secretly intended to use Rio as his candidate to embark on the Infinity Path and become a "Destroyer" who would reduce the world to ruin.
Eventually, Long would succeed in molding Rio into his destroyer after Rio was defeated by GekiRed and his anger over losing caused him to awaken as the Destroyer. However, Rio was deconverted from his transformation by his own right-hand Mele and his love for her. With Rio no longer the Destroyer, Long attempted to finish off the Gekirangers and Rio so he could find a new candidate to be his Destroyer, but was destroyed by the Gekirangers.