Points of Reference
In Makai, Yusuke discovered he didn't know himself.
It was so tempting to blame it on his recent--well, what would you call it. His transformation. His change of allegiance as to genus, species, etcetera. His psycho new hairdo.
But he knew that wasn't it. He knew that wasn't why the monks were exasperated, why Raizen's distaste for him was starting to show--Yusuke wasn't sure which was worse, not having a dad or having one who was disappointed with you--why he was frustrated and angry with himself, grasping for something that wasn't there. Genkai would have said he was half-assing it, and she would have been right. Yusuke found himself unable to do anything, anymore.
Maybe he had never really known how to handle things. After all, when he'd finished that first round of training with Genkai, back when being Spirit Detective had been a novel concept, he'd gone straight into the Maze Castle case--then they'd rescued Yukina, and then the Dark Tournament, and right after that Sensui... And never once in all that time had Yusuke been alone.
He realized now how cocooned he had been. There had always been someone behind him calculating a way around his latest mistake, and someone ready and able to slip in and end things given the slightest hint of an opening, and someone willing to barge in without any opening at all and damned with the consequences. Yusuke hadn't ever realized--no one had ever realized--that he could only do the things he could do, defeat the enemy no one else could defeat, because he knew he had one hell of a backup plan.
Now, Yusuke was not as strong, because there was no one to show him what true strength was like. He was not as free with his trust, because there was nobody who needed that trust, needed it so desperately that he would give everything in exchange for it. And he was slower to sacrifice himself in battle, because now there was no one so willing to die for them all that Yusuke had to be just as fast as him, needed to match that sacrifice or lose a friend.
It wasn't just his fighting that was suffering. He constantly felt lost, off balance: like he was standing in the middle of a glassy black plain with no points of reference to orient himself around, nothing to let him know which way was up. He slammed his door shut just as often as ever, but now there was never anyone hovering on the other side, wondering whether to knock. He was simply alone, depressed and wondering if he'd ever been able to do anything, or if he'd just taken the best parts of his friends and cobbled together a personality from them. If he'd ever actually understood himself, or simply relied on their interpretations of him. It was hard to start from scratch again.
The mirrors in the castle weren't nearly as kind as the reflections he'd seen in their eyes.