Sans finds himself grinning with genuine mirth at that response, and something about it feels peaceful and right. Yet, when his own reaction occurs to him, he finds himself inwardly doubling back. He's leaving himself really exposed to this person.

As they've just reminded him, fighting is definitely something he remembers them doing, the glowing soul included. So while he keeps on grinning, as he always does, that genuine lining of pleasure fades off.

"...Say. This might be crude to bring up apropos of nothing, but...truth is, it's been rattling my bones for a while now." His stance settles into something more guarded, his hands tucked back in his jacket, ready to move if the response is negative. "You really seem to have this all figured out, don'tcha, kid?"

The lights in his eyes seem to go dead.

"Mind telling me why I remember killing you?"