The story is entertaining, sure. Fast-paced, amazingly creative, dynamic actions, etc. But the plot tries to include such much meaning and so much characters that character development is lacking at the end of the day, even with 27 volumes. Yes, Shimizu-san is a definite fan of amazingly handsome and prestigious characters who attract people with everything about themselves: their face, their professionalism and even their FRAGILITY. This is key; the thing that either makes or breaks this manga for most people. Shimizu-san wanted to ultimately comment upon human nature; she wanted to explore whether even clones, who had replaced their genetic twin were entitled to their new, prestigious lives or to the hate they felt for the world. These people, these "donors" were basically a part of Akira's reverse-harem because of their pull to her by faith, and yet she was trying to appeal them to the readers by their dedication to her and their fragility.
It makes NO sense. Here are people who let a huge part of one's life - their love life, and really, all of their life, rely on "fate". Their attraction to Akira; they all swore to protect her infinitely; her pull on them was absolute. The fact that they accepted that so readily was already counterintuitive to the reader; I mean, they were frothing angry at having humans having created them as spare parts but they weren't angry and Kaguya Hime for making them bound to Akira for her revenge? Why? Because Akira's a very attractive girl who's also very fragile?
Honestly, the series really boiled down to a whole bunch of half-developed donors surrounding Akira whose sufferings were rather entertaining than solemnifying. No one could relate to her tantrums, her obsessive attraction for that one girl she grew up with, or why she chose the guy from the Moon; it was more like, at times, Shimizu-san threw us reasons, but we couldn't relate to them with our hearts. Akira seemed more like a selfish and pathetic girl. And the donors; even once they started to show signs of real "humanity" towards the end, it was unexpected and unwelcome because the one defined character development we got from them had been their love for Akira, which is real, was the only redeeming factor shown.
Seriously though. I think Shimizu-san's desire to have a really good manga was blotched by her desire to have Akira as an absolute femme fatale. The girl she grew up with was obsessed with her, all the donors were obsessed with her, the moon boy was obsessed with her; and usually, I'm amazingly flexible with well-off characters because I reason that that prestige isn't something that negates the reality of their struggles, but this was just ridiculous. Everyone was vying and messing up their lives for her, and she, totally ambiguous and wishy-washy and useless, messed everything up.
What saved this at least was the prince, and the ending. The prince (or king... Whatever...) was the one rational character in this entire thing. His love for Akira was, I think, the only real one, because he didn't feel the need to wave it around as a torch or sword all the time in front of everybody. And the extent to which he quitely understood her and watched by her was admirable. The ending was, in a much more Shimizu-san like fashion that I could appreciate (read "Himitsu" by her; it's an absolute masterpiece), bittersweet, inspiring of reflection and awe, morally complex, and sobering.