
What is this?!?
(please use keywords, and keep guesses under 50 characters)

Lawyerbot was attempting to organise his Usuki collection and came upon a box with 63 Deluxe Angel Usukis and 113 Devilish Usukis inside. He also had an additional 72 Devilish Usukis next to him in a bag. Then, his programming went a bit haywire.
Every time he'd reach into the box, he'd pull out two Usukis. If they were different, he'd toss a Deluxe Angel Usuki back in. If they were the same, he'd toss a Devilish Usuki back in. He kept doing this until there was only one Usuki left in the box.
Which Usuki was it?