One of the Fuujin oni's eight original demon followers, Gerozaemon got stuck in a frog's body after his reincarnation—and basically just became a frog from then on.
He was the first demon sent to deal with Yaiba, leading a handful of attacks against Yaiba's crew before getting beaten and captured. Things went downhill fast: the Snakeman demon showed up, kicked his ass partly just to get rid of what he saw as dead weight, and Gerozaemon found himself with nowhere to go. Good news—his surprisingly chill nature meant Yaiba's group was happy to take him in after they dealt with the Snakeman threat.
In a fight, Gerozaemon's go-to move is body-slam attacks straight out of sumo wrestling. He can handle an axe well enough, and he's not above using his own tongue as a weapon either when it comes down to it.
Content compiled by AnimeList.moe from publicly available sources.
