This manga was much better than I thought it would be based on the description and the first chapter. The setting is dark and convoluted: you have innocent kids who are removed forcefully from their families and trapped within a compound, their letters to their families are burned, and some are forced to perform unscrupulous missions outside the compound to the detriment of their health. Some of the teachers care about the students (yet mostly turn a blind eye to the school's policies) while others simply use them for personal gain. Meanwhile, the students are plied with bread and circuses and given advantages and better food based on their obedience. They only have other students to depend on, so they form strong bonds that in essence keep them trapped to the school in a kind of stockholm syndrome type of way. The author does a great job at depicting this creepy atmosphere, and the innocence and gradual loss thereof of Mikan.
The romantic development between the two leads is one of my favourites of any manga as it portrays so well the way in which their conflicting personalities and experiences eventually reconcile. My favourite parts are when they're sitting in awkward silences and Mikan is feeling stifled and confused, because I don't think I've ever seen this type of experience portrayed so seriously and so well in manga before. As for the rest of the romance though, I really disliked it. You get two instances of grown men impregnating teenage girls, and two instances of a man being hopelessly in love with a female for a ridiculous period of time and then becoming a replacement when her boyfriend dies. I kept wanting to say, 'IT'S BEEN EIGHT YEARS, GET OVER IT' or 'YOU'RE ELEVEN, GET OVER IT'. But when you fall in love in this manga, you're never allowed to fall out of love NOT EVER.
There were a ton of characters, which I don't mind, but some definitely got forgotten in the later half. This may have been because their alices weren't condusive to the plot (it seems like the class rep would have been awfully useful during the fighting) or just because there were too many others to keep track of. I wanted more about the 'dangerous' class too, I felt like it could have been more interesting than it was.
I didn't mind the ending as much as many of the other reviewers did, though I didn't like the last image (because of what it implies). It was a sad ending IMO (again, because of the implication) and the manga was also pretty depressing, which is to be expected from this kind of setting. I got teary through most of the second half, probably like 50+ chapters. I'm an easy crier, but yeah, don't read this manga if you're just looking for a nice romantic comedy. There's some good comedy, but overall the story is a serious one.