Already in a cantankerous mood- catching Crowley's offhanded comment wasn't helping to alleviate that. At least the only response he offered up was a quirk of an eyebrow as he briefly scrutinized the stranger. Kaiba had fully intended not to engage this man in an unnecessary conversation, since he already had problems enough of his own without adding to them. How he both tired and loathed people trying to drag him into their humanitarian endeavors. That and when they tried to convince him of the existence of magic. Magic. Who were they trying to kid? It was insulting really and this place had already touched on both of his triggers. Let the Kingdom deal with it's corrosion problem on it's own, he had a business to run and a younger brother to watch over.

So no, he hadn't planned on even acknowledging the winged idiot but that was before Crowley just kept talking. That was when something within Kaiba snapped, and he came up with a sarcastic response. He was never really short on those.

"If I had to guess, I'd say it's for the same reason that you forgot to ditch that ridiculous costume."