^Well, it's fiction, after all...
I really doubt, for example, that Ayu got her debut by winning a 10km run with her sholder dislocated. Not because I doubt she would try something like that, considering much she performed injured and in pain over the years, but because this doesn't make sense as a singer selection, even if that would explain why jpop stars tend to be so bad at singing, as that wasn't evaluated at all lol.
In the end of the day, I believe they are showing both under favorable light without making they feel unhuman. I like how it's being constructed that Ayu didn't made it because she was good, but because she was resilient.
It would have been fun having a major soloist under the TK inspired character, and a big rival from another company once Ayu debuts.
The worst part still is the reproduction of iconic performances. Karen has no stage presence and everything looks cheap as fuck.