There is a split-second where the look on Kaeya's face almost resembles the one his younger self wore, when he heard his brother calling for him and he didn't know whether or not he should go to him rather than hide. It's hard to pinpoint what it is exactly, but the closest thing is a feeling that overwhelms you when you realize you've lost your way.

"... Then, if you'll excuse me," he murmurs quietly, quick to look away in case he is betrayed by his lack of composure once more. "I'll try not to get in too much trouble while I'm there."

And there he goes. He won't say thank you out loud, but he doesn't think he has to.