From the introduction:
In a distant swamp in the interior of medieval Japan, in a small city called Mizutamari, lives a society of frogs built around dynastic swamp lords and amphibious warriors beholden to oaths of honor and revenge. NUMA is heavily inspired by the graphic novels Musashi by Eji Yoshikawa and Vagabond by Takehiro Inoue, Akira Kurosawa’s samurai films, OSR RPGs, and oriental batrachians.
Players in NUMA take on the roles of young samurai frogs (samurai gaeru, or furoggus), devoted to a life of duty and fighting, and charged with protecting their realm from those who threaten peaceful life in the swamp.