Shirou looks a little embarrassed by that. He considers the arm and pokes the red binding that covers the entire arm thoughtfully. He already knows not to mess with it, but it's still weird to realize others might point out the strangeness of it all.

"I'm still getting used to it... But, eh?? What do you mean 'substitutes' I already lost the arm once, I don't really want to do it again." Once was more than enough.