Just finished this up and I've got to say this was one hell of a ride. What started out as a generic romantic comedy grew into something much, much more. It's one of the few mangas I've read which is successful in juggling so many different themes and ideas while still remaining true to the central story. In here you've got love, of course, but as the books progress you're also dealing with themes of violence against your fellow man, sibling jealousy, loss, death, rebirth, and even the very existence of God. It's quite a bit to take on, and yet the mangaka is able to successfully blend all these elements and create an entertaining story that kept me captivated from start to finish.
Of special note are the characters. Like all of the very best manga, Takeshita spends a lot of time fleshing out not only the two main leads, but much of the secondary cast as well (my favorite being the Yuria/Shishio subplot that runs through the course of the volumes). He does an excellent job of making you care about all the characters, while still being able to tie their stories into the central themes he's exploring. Fantastic writing on his part, and I've really got to commend him for that.
The artwork starts off a little choppy, but he seems to find his stride after a couple of volumes, and from then on it really takes off and works well with the story. It's still a bit of a quirky style, but as I said it works very well with the story and I liked it.
I've also got to commend the mangaka for the books ending. It's a fantastic way to wrap up the story and it definitely brought a smile to my face. While it doesn't answer every question that was posed, I believe that this was done on purpose and it actually works well within the context of the story and everything that's come before it.
I'd also like to give special thanks here to pew pew for picking this story up and running with it. This has been sitting in scanlation limbo for so long I wondered if any group would ever finish this up. I would mention this title every chance I could when talking about projects that needed to be worked on/finished, but while many people seemed to agree with me it never seemed to get beyond that stage. Not only did pew pew dedicate themselves to actually finishing this up, but their release schedule was nothing short of amazing.
Still, in the end, this one is kind of difficult to know whether to recommend or not simply because it encompasses so much. It covers so many different themes and genres that It's hard to know who would enjoy this and who wouldn't (for example, you may enjoy a light harem comedy, which this is, but not be particularly fond of books with deeper religious themes, which this also is). It's a little bit different, but for me that's something I really liked about it. Fantastic characters, great, great storyline and a well thought out ending make this one something very special. So if you're looking for something a bit different from the norm, I highly suggest taking a look at Happy World!
9.5 from me with the only weakness being some of the less than stellar art in the first couple of volumes (believe me, it gets much better after that!)