Ken is only moderately difficult to find. It's not that he's making himself easy to track so much as the inevitable byproduct of Ken losing his temper - and not having Mukuro or Chikusa, or some kind of orders, to check him - is a lot of freshly tenderized semiconscious bodies in his wake. Judging by the claw marks on the people Chikusa finds - mostly thugs in alleys, in the more questionable parts of town; it's hard to tell if Ken's restricting himself to trouble areas and troublemakers because the commotion's less likely to be noticed and he's still conscious of not complicating Mukuro-sama's life, or if he was just spoiling for the easiest fights he could find with the people most likely to put up a fun struggle. The two things aren't necessarily mutually exclusive in any case.

Considering he's only had a couple hours to work, it's impressive how many people Ken's gone through. It looks like the better part of at least two gangs, closer to 20 people than 10.

Chikusa will eventually find Ken stretched out on the lowest landing of a fire escape, either temporarily sated or catching his breath. He appears to be still in Wolf Channel, but despite the fact that he must've smelled Chikusa coming, he doesn't acknowledge his presence for the moment.

...actually, there's also the possibility that he's dozing. It's impossible to tell from this angle if his eyes are open or not.