4000 years ago a style of martial arts was developed that mimicked the abilities of animals, Juken. Three of its ten masters developed Rinjuken to draw strength from the suffering of others, the remaining seven created Gekijuken to draw power from within oneself. The Rinjuken masters were ultimately defeated and sealed way.
In the present day Rio, a former Gekijuken student revives Rinjuken amd fallen Rinjuken users with the goal of world domination. Master Sha-Fu nad been traini g to young people to fight Rio, together with Jan, a feral boy they become the Gekirangers.