K9999 is considered to be a boy not to be tampered with. He has a very short temper and is easily driven to violence. He hates K' with a passion and intensity, and considers him his ultimate rival. Most of the time, K9999 despises everyone around him, including his superiors. In a fight, he attacks with such ferocity and strength that, at times, he doesn't even mind being hit, as long as his opponent falls to the ground. He is a cyborg created by NESTS.