by his partner, Dracmon) has black hair and first appeared in Book Six when Sakura ran into him (literally). His usual outfit of black jacket, black pants, and a blue shirt has led his partner to also refer to him as "Mr. Black and Blue." His D-Vice is mostly grey (a trait so far associated with Demons) and orange. He might not have the best relationship with his digimon (insults, humiliating questions, and even payment to the rookie have all been problems the boy has dealt with so far), but they've made some progress since he first met the digimon as Sangloupmon and tried to ride him.
He and Sakura have remained aloof from the mainstream tamers, uncertain of how they would fit in or even if they would want to be involved with the main group. This distance from the known group of tamers is one of the main reasons Rayleigh Thompson's plan doesn't seem include him or Sakura. It is quite likely Rayleigh Thompson doesn't even know of the boy's existence.
One of his first battles against a Devidramon left scars on the boy's face when the champion struck him, but the boy survived relatively unharmed. This strange resistance to injury is generally an Angel or Demon trait, but Kohaku has yet to demonstrate which group (if either) he will eventually become a part of.