ED collection on the way, to be issued in July. Since it says "dorama," I suppose they'll string it together from the show, with maybe extended versions of the songs. Not sure.
Vexx is certainly right about seiyuu, and that includes Aya. My favorite singer in the world is Onitsuka Chihiro, who is (or at least was) superior in all respects to any seiyuu singer I know of. And
Wavedash is right about the technical points he mentions, although I would of course put it a little differently, lol. But those are, within limits, immaterial to my own enjoyment. I'm getting sweetness and some feeling, as well as real melody. As in some of her seiyuu work, the fragility of it all is also attractive.
I have said before that I think originality is overrated. I'd say the same for professional skill. I think seiyuus who are "professional" can sometimes be boring, and the same goes for singers. I don't know if Kotoko is considered skillful, but I find her work quite boring and unsubtle. Of course, the same goes for bands. Garage bands can be more enjoyable than top pros.