It's not what he expects and Rat watches him for a moment. It's hard to choose which reason makes him most cautious. That he's loved and lost in too much measure. That he isn't in a mood to fight off violent reprisals if this goes badly. Maybe it's that he does have a measure of respect for Kaz he isn't eager to see damaged.

Whatever the reason, it gives Rat cause to be careful as he reaches out and lays his fingertips against Kaz's. It's a feather light touch, easy to escape, but it is there.