...Were we? [His tone is something approximating neutrality, too controlled for outright genuine confusion.

He's surprised, but again, not in the completely dumbfounded way. Surprise, yes, in that he's hearing something he hadn't expected to hear. Surprise in hearing it from Sans, and getting confirmation where there'd been uncertainty. Controlled, in that there's something he's not rushing to share either. He makes another contemplative sound, then offers:]

Is that why... sometimes people seemed, familiar. The first time I met them. Like we were always meant to be friends...