An ape monster that leads the Devil Beastman Ninja Corps. Gynaninpo wields an extending staff in battle which he can shoot beams from. He can also assume the form of anyone he chooses. After the Devil Beastman Ninja Corps attacked a mountain village and captured its inhabitants, they and Gynaninpo attacked Kotaro and Reika while they were in the woods though they were saved by Joe. Joe infiltrated the building that Bosgun had the prisoners in by disguising himself as a Devil Beastman Ninja, until his coughing gave him away to Bosgun and Gynaninpo. Gynaninpo took out Joe and assumed his form. Gynaninpo sent the Devil Beastman Ninja Corp to attack the place where Kotaro and Reika found the kids taking refuge. Kotaro fought them until "Joe" defeated them and led them to where Bosgun has the prisoners. After Kotaro found the real Joe, Gynaninpo shed his disguise. Bosgun revealed his plans to Kotaro and left as Gynaninpo and the Devil Beastman Ninja Corps fought Kotaro. Kotaro transformed into BioRider and freed the prisoners. BioRider and Gynaninpo fought outside as BioRider destroyed his Devil Beastman Ninja Corps. He then called for Mach Jabber and charged him. Gynaninpo climbed a cliff and attacked BioRider, but he turned into water, attacked him, and knocked him off the cliff. BioRider reverted to Kamen Rider Black RX and used his Revolcane to disarm Gynaninpo before destroying him. Gynaninpo was later revived by Maribaron as part of the Spirit World Inhumanoid Army and even impersonated Kamen Rider 1.