Kylo is more than a little grateful for Vader taking the lead on inviting Rey into the conversation. Positively radiating it. All he could have done is stare at her, or make himself come up with words that would inevitably be wrong.

He nods after his grandfather speaks, and gestures toward the makeshift seat that's been made for her. Now that he's had a moment more to consider, he can offer her at least the beginning of an answer. "That feeling you mentioned. I think I know what it is."