"Calculated chaos" isn't paradoxical. A paradox sounds impossible, but can still be possible. The way you explain it, it's an oxymoron that's there without a good reason.
Also, "mental power" can't exactly be self-explanatory (magic in general fails to explain itself), but from your description you should just be calling it energy. Calling it "mental power" sounds conceited (which is a problem we faced with Mimi and how he worded everything in his sheet) and completely removes any potential for physical consequences (which Colony and I forgot to touch on in our original response). Many of the accepted characters are capable of killing themselves outright for slipping up, and the absolute worst that happens to Yukio from using magic is that she just passes out.
We didn't completely bring this to light either (but it seems appropriate to at least do so now since you have to expand on her anyways), given how you describe her in both the personality and history, Yukio would be utterly useless in an actual fight due to anxiety (because if a mage battle isn't hectic and chaotic in some form, then it's not much of a battle), and there's no development described whatsoever that tries to improve on this.
Lastly, yes, being concise is generally a good thing—I can understand where you're coming from with it in being straight-to-the-point—but don't sacrifice very necessary information and development just to save space.