Evil-Oh

Evil-Oh is a clone of Riki-Oh created by Dr. Kohinata tasked with killing him. He appears identical to Riki-Oh, but the primary difference between them is that Evil-Oh is over double the size of Riki-Oh. He was designed to be superior to Riki-Oh, and claims he is twice as strong and fast while being able to use all of Riki-Oh's abilities. He is undoubtedly much stronger than Riki-Oh, able to overpower him multiple times and using a tree as a giant battering weapon. He is apparently able to punch faster than Riki-Oh can see.

Evil-Oh's personality is, unsurprisingly, evil and psychotic, as he is shown to kill a trio of hunters for no reason. This could have been done to lure out Riki-Oh due to his heroic nature (A tactic several other villains use against Riki-Oh), but it is just as likely that Evil-Oh was being evil for the sake of it. Evil-Oh is convinced that he is the real version and that Riki-Oh is the fake, and this quickly becomes his primary motivation for fighting him as he wants to prove that he is the better of the two.

While Evil-Oh has free will, Dr. Kohinata is able to override it if necessary by playing a violin that enables him to make Evil-Oh do whatever he wants. Somehow, playing this violin allows him to control Evil-Oh from any distance. Kohinata gives Evil-Oh some combat instructions given he is a less skilled combatant than Riki-Oh, but eventually Kohinata breaks his violin strings which meaning Evil-Oh can no longer be given any instructions. The violin can also apparently be used to heal any damage Evil-Oh takes.

Aneyama and Kohinata are able to watch Evil-Oh's fight against Riki-Oh through a camera inserted into Evil-Oh's eye, with Aneyama regularly threatening to kill Kohinata if he loses. At one point in the fight when Evil-Oh clearly has the upper hand, Aneyama tells Kohinata to not finish off Riki-Oh too quickly because he wants him to be tortured first. Kohinata makes Evil-Oh hold back at this point, meaning he could very well have been better off without any instructions and instead fighting entirely on his own.

While not as skilled as Riki-Oh, his general intelligence is around the same level as him, as he does manage to outsmart him, even without any instruction from Kohinata. Evil-Oh traps himself in quicksand and demands Riki-Oh save him, saying he was only just following Aneyama's orders. While Riki-Oh does not believe his words, he gives in when Evil-Oh starts crying as his good nature prevents him from leaving Evil-Oh to die. Evil-Oh grabs Riki-Oh and drags him into the quicksand in an attempt to kill them both, and is very nearly successful.

According to Dr. Kohinata, Evil-Oh is the "subconscience" of Riki-Oh. Its implied that he was able to replicate Riki-Oh subconscience by gathering info about his past and power, just like the Guards on the Cape do. Hence Evil-Oh represents the selfish and evil desires of Riki-Oh´s mind.

After Evil-Oh dies and their bodies fall through the quicksand, Riki-Oh carves a way into his body to hide to survive the fall. Riki-Oh tells Kohinata that the "fatal flaw" in his design was making Evil-Oh much larger than him, as apparently being able to hide inside of his body was not worth the advantages of strength and speed given by size. Kohinata later activates the self-destruct function on Evil-Oh's corpse.

Evil-Oh's size showcasedEvil-Oh uses tree as clubEvil-Oh lifts a gigantic boulderEvil-Oh uses crocodile tears to trick Riki-OhRiki-Oh stupidly falls for Evil-Oh's trickRiki-Oh bursts out from Evil-Oh's corpse