On your way to the Core, Sans asked you if you wanted to grab dinner with him at the MTT resort. You obviously agreed and he got both of you there via 'shortcut'. Right now, you're sitting at a table, right across from Sans in a purple-ish room and a dimly lit candle in front of you.

"Well, here we are. So. Your journey's almost over, huh? You must really wanna go home. Hey. I know the feeling, buddo. Though... maybe sometimes it's better to take what's given to you. Down here you've already got food, drink, friends... is what you have to do... really worth it?" Sans asks, alluding to the fact that you have to kill Asgore in order to leave.

"..."

"Ah, forget it. I'm rootin' for ya, kid. Hey. Let me tell you a story..."

Sans then talks about his experience with meeting the 'woman behind the door' but that's not what catches your attention... it's the thing he says after that story.

"Do you get what I'm saying? That promise I made to her... You know what would happened if she hadn't said anything?... buddy. . . . Y o u ' d b e d e a d w h e r e y o u s t a n d... Hey, lighten up, bucko! I'm just joking with you. Besides... haven't I done a great job protecting you? I mean, look at yourself. You haven't died a single time. Hey, what's that look supposed to mean? Am I wrong...? Heh. Well, that's all. Take care of yourself, kid. 'Cause someone really cares about you."