The flinching isn't anything unusual; Isaac doesn't even notice it anymore. He's very pleased with Kimblee's words though - no, he doesn't think Kimblee sees, but it's alright, because he doesn't really get it either. But Kimblee's not angry with him, which means he hasn't ruined this relationship (somehow) and that's such a relief...

He tightens his grip momentarily before realizing what he's doing. Isaac forces himself to loosen his grip. There's no need to crush Kimblee, after all. That would be kind of counterproductive to this whole "you're not leaving" thing.

"Thanks," The word is rushed, nearly breathless. "Thanks." He's obviously very grateful for it.