Takoshi (Octopus Death) is the villain in the Yakimon world. An evil deformed genius who wears an organically engineered octopus helmut. He is a master of genetic engineering. His masterpiece being a species of Ikakumora, spider/squid hybrids to do his bidding.
 Shishi is the protector in the Yakimon world. He can only be summoned by twin boys, Ichiro and Jiro. Shishi was once two powerful beings, but became one after being attacked by a horde of Ikakumora while in the process of being summoned. In order to save the injured one Shishi recombined as one.
 Ape is just a total dick. He roams around causing destruction, seemingly fighting for no side, but his own. He can rip off his own body parts and replace them with what ever objects he finds amusing. Likewise he can attach his head or limbs to another decapitated or dismembered body and reanimate it. There is still so much secrecy shrouding him and it is rumored that there is some mad creator behind his existence.
 Ikakumora is a genetically engineered minion created by the disturbed mind of Takoshi(Octopus Death). It is a cross of a Spider and squid. They range in size from giant to mini and are bred to have unique abilities. Abilities range from toxic poisonous bites to sticky ink blob projectiles. Being a mix of spider and Squid they can maneuver easily both through water and on land.
 Feejee Fighters are protectors of the sea. They fight for whatever side they deem beneficial to their cause. Sadly they are quite gullible and easily tricked. They are fond of throwing poisonous urchin at enemies and as well like fashioning crab claws and other discarded ocean debris as arm weapons.
 Every story needs a devil spawn right? Mutton Chomper was the Beasts attempt at creating the ultimate demon possessed cyborg to finally crush humankind. As with all cyborg AI stories though Mutton Chomper had other plans of his own. Why care about the domination of one simple world for a single minded ruler when you can dominate the known universe by yourself.  How does he fit in the world then? Its his home base where he goes to chill out.