[ Ah... In the face of Undyne yelling at him, his humor does deflate, but he still shrugs rather dismissively. He doesn't deny it in the slightest, and he really doesn't even seem that sorry about the idea of doing it. Instead, the softly apologetic smile is more because it's making other people upset now. ]

...I think you've had a bit too much faith in me, Undyne. I'm not exactly a noble person.

[ He pauses, but then he at least decides to add: ] But for what it's worth, I'm glad that things turned out this way, even so.