God damn you guys are posting too quickly I can't keep up!
Well for one, I'm glad you guys liked Yuzuki's backstory, second I'm surprised no one has considered that she might be a tad OP in her current state, since arne't Youkai suppose to get stronger the older they are, and she's what she's over 800 Year's old, heck she's even been in Gensokyo since the Great Hakurei Barrier was formed! Even if she was just passing through when it happened :V
Though the main thing that makes her OP is her age, as she has learned quite a lot about magic in her lifetime, learning all about magic from different parts of the world before being trapped in Gensokyo, and due to all her travelling, her magical powers have become really quite potent and powerful, so much so that even everyone's favourite overpowered sunflower youkai Yuuka would have some trouble in a fight with Yuzuki, but I do have a plan in mind to resolve this, though I'll leave it for when she makes her grand entrance into an actual Scenario in the game itself
as for why I didn't touch her stats, mainly because I wasn't sure what to do with them at the moment.
As for Spellcards, well due to Yuzuki being in isolation when the spell card rule was created, has pretty much no idea that such a thing even exist, and one thing Yuzuki hates, is having her power limited so when she does find out about the spell card rules, she ain't exactly gonna be too chuffed about it and will probably just outright refuse to use em, though how she comes around to the idea of using spell cards is tied in with what I have in mind for resolving her OPness.
As for the traits, I think I have something in mind that could work for her.
That's the other 50% of my trouble. I'm sure I can get some inspiration from playing Disgaea or something. They've got just the kind of humor I like using.
Disgaea, fuck yeah!