Sans doesn't startle at Papyrus's outburst, but he does turn to look at the shadow of his brother more carefully. It's interesting to see how much of that frustrating is deep and sincere.

"It's easier to hate than it is to change, bro," Sans says, quietly. "I could't do what I needed to do, and the failure shook me. I started to hate myself, and then I hated myself for hating myself. But... when you don't feel like anything can change, the only way you can make up for what you've done wrong is to let yourself suffer for it. Cause you feel like it's what you deserve."

"But you didn't deserve that," he says, glancing over with a couple of his eyes, disconnected from the ones staring ahead. "If I fell completely, I'd be dragging you down with me. So, I just tried to mitigate things by having zero expectations. Y'know? Can't be disappointed if you never hoped for anything in the first place. And I didn't want anybody to hope I'd do anything useful, either, if I was just gunna let them down."

He falls silent for a few moments, making a connection he never had before.

"It's kinda like the next best thing to not existing. If I showed how bad I felt I'd be hurting people around me, so I just did a bunch of pointless bullshit and acted like nothing that happened actually mattered. Even if it did. But then I came here, and I ended up with all these responsibilities... I can't just be a non-entity anymore so I have to try to be something else."

"All these people count on me and if I'm not good enough to do it, then... I don't know. I end up wondering what the point in being anything is."