Don't apologize for something like that.

[He takes in the other boy's condition in a glance, worry becoming even more apparent as his brows knit together.]

Undyne is some kind of... fish lady, I don't know why you thought you'd be able to keep up with her in the open ocean.

[But he offers a hand, pointedly not looking toward Nagito's left hand. Please don't put the stump in his hand, that'd be a little weird.]

C'mon, you can lean on me. I'll get you to the medbay.