"...felt longer," he finally admits with them. It was a life. Another life.

The meaning behind what Frisk says next is unspoken, but entirely obvious. Not a good look for them, either, and one that he finds himself wondering just how much he had a hand in. He's been there, and thought that. They taught him better. Maybe he can do the same for them. Maybe it can work like that for once.

"yeah, well, i wish it wasn't you chained up down there." Trying to imply that they both suffered, and that neither of them is the one to blame for that. It's a surprisingly sensible view, for Sans, but it's always easier to share good advice rather than follow it. He heaves a sigh, and adds: "so it looks like we both got kinda boned in this mess."

He pulls away just enough to see if the pun has had any effect. And throws in a subject change for good measure.

"you know that we're forgetting something, right?"