[Because sometimes ninja friends get startled and try to stab you. That worried expression only grows more and more concerned as Hershel speaks, however.]

I... can't really imagine you killing someone, either. [It's Hershel. Hershel. Calhoun had to be lying.

Him, on the other hand...]

...Even if attacking Yuusuke was just an accident on my part, I just--

I don't know. [And that's what's got him so agitated. He knows now that he is probably far more capable of badly hurting someone than he's really comfortable with. Killing someone wouldn't even be that much of a stretch. And he still doesn't even know why he's able to do any of it.]