Her prayers ease the pain, and for that Sans is more grateful than he would ever be able to express even under normal circumstances. It doesn't even occur to him that she doesn't feel them doing that much work. Then again, everything else that's going on is rather distracting.

But she can't stop it. As far as Sans knows, nothing can. It's a miracle that he's even been able to hold on to his own shape for this long, but...he knows what's happening, this time. He didn't before. And he knows that there are people that need to be warned.

"Might be dangerous...might forget stuff...y-you'll keep 'em safe, r-right?" He doesn't specify the "them". He doubts he needs to, by now.