Prospero actually saw Naoto's strategy the second he started wrapping his hands, but he had also noticed something much more pressing and interesting. Even if it was only for a few seconds while the young magician was running three deceptions at once, the future Vongola Boss had somewhat pierced the illusions and figured out that both his tactics and the disappearance of his friends had all relied on tricks and misdirection. 

Clearly the eleventh Boss candidate was sharper than Prospero had initially given him credit for, and his own ability with illusions was still weaker than it had to be. As a magician who staked his livelihood and his pride on an ability to read and trick others, he considered an error that complete to be both rare and inexcusable. Furthermore whether Naoto had already realized it or not, Prospero had said that seeing through his tricks was one of the possible conditions for a 'victory' for Naoto, and the masked boy intended to stand by his word.

Unfortunately, he had also underestimated exactly how fast Naoto could attack him. Before he could even mention that Naoto had already won, the soccer star was rushing him. While Prospero's training certainly gave him decent reflexes, between preparing to end the fight with an explanation and maintaining the illusions he was totally caught off guard. He flailed with the cane without thinking and got caught in the feint Naoto had set up, ultimately getting knocked flat on his back while painful, painful stars bloomed up in his vision. However, in the end being fooled and losing so thoroughly for the first time in years left just one thought in his head.

[i]That...was really, really fun![/i]

As the illusion faded out and they both returned, Prospero started laughing. Not the sort of low, evil chuckling that he'd gone for before but actual, happy laughter. He had assumed he was in for yet another disappointment with his little test for Naoto, and his expectations wound up being exceeded. Sure, it meant that Prospero himself was much weaker than he'd thought, but for the first time in years he finally had some direction. Better yet he'd gotten to play around with someone interesting while acting like a ridiculous villain, even if they didn't see things like that, plus if everything worked out he would no longer have to work towards revenge alone. He couldn't help but laugh in joy.

"...You know, you're actually a lot of fun! Saying stuff like 'Don't underestimate me!' and charging in all concerned for your friends? Pretty awesome! Anyways, don't go thinking you beat me outright, but I promised you answers if you could see through my trick, right?"