Let us look at Kassy here, a few questions come to my mind.
First of, what kind of people just disown a child whom they took into foster care for something she couldn't control? Despicable.
Now, I don't know too much about fourth dimensional powers, but I would consider it a science! Not, "magic" And as an added, how does Kassy protect herself during this coma? Essentially she became unconscious, and was moved to a hospital where she spent an arbitrary number of years there, her emotional growth and maturity would likely be stunted from such an occurrence.
What made her interested in this convention?
^ Those were really cherry picked by the way.
As for Naoto, I think everything appears in order for him. And I assume that he took part in a procedure in order to gain his power.
One thing that needs to be stated, there should certainly be a logical reason for every single character to be where they are, and doing what they are doing. Plain and simple.
I think, in terms of Kristof's muscles, it would be unfair to deny. The problem would be that, are we to say that there are no men like Kristof? Even stronger still, I'd say that a relevant back story must explain any extraordinary talents or abilities. The bottom line is logical sense.