You're not sure if you can take one life to save others.

[He states it casually, and that's probably the most annoying part. As if he's disregarding Sheena's other words, and like this isn't important. Of course, it only seems that way. He cares. Of course he cares. That's why he's here, after all.

But it's better if she doesn't pick up on that.

The point is she's worried and stressing out about it, and he wants to reinforce that it's not wrong to think like that. That she shouldn't do anything she regrets. He's just not sure how to go about that himself... So here he is, probably spurring it on.

But in the end, he's positive Sheena will sort things out. She doesn't really need him. She just needs a gentle nudge.]

Haha, well you're right! There's no way you're going to be able to do it.