That really is very much like Senku. Just those few words - that he's inclined to protect the people who help him. No matter how much Senku may struggle with emotions, or stuff like friendship.. or how differently he expresses it than Inigo himself, Inigo still knows this much is true. That Senku isn't uncaring, that would stick his hand in the fire for others if necessary.

".. Thanks."

He smiles as he says it. There's genuine gratitude in his voice, since he just thinks it's sweet on Senku's part. And Inigo can always admire it when people care about each other.

"Still not going to throw you under the cart though." Sorry, Senku!! "But.. take it easy for now, yeah? I can't imagine it was a very pleasant mission with all of that happening."