tl;dr: A manga that tells two separate story threads that eventually collide, with one being well written and having a lot of emotional impact, and the other one being somewhat of a mess.

There was more to this series than I thought there would be, but not really for the better. The main story is about a guy, Ikuru, who's dying living with a girl, Ai, who was born in such a state that she's dying. They comfort each other and do their best to find happiness despite this. They also interact with various other characters who have stories and morals of their own. This was an incredibly well told story, with lots of really cute and really sad moments that really tugged at the readers heart strings. It also conveyed strong messages related to life and death, mainly that death was inevitable and that while that would never be something that people can come to truly accept, it was something that it was possible to live with and continue making the most of one's life with, even leaving something of value behind. This may seem cliché to a sense, but it felt like it was saying this in a way a bit different from most takes on this, and it had a good amount of impact. What adds more to the story is that this is all taking place in a future that is semi-apocalyptic with all sorts of crazy things such as aliens as saviors and the end of human evolution being touched upon mainly focusing on the secretary general of some organization dedicated to protecting humanity. The problem with all this is that except for how it set up the ending, it felt completely separated from the main story, both in terms of plot and tone. Furthermore, that side wasn't all that great. It said a lot of profound sounding things, but it didn't really establish them or give them any meaning. It had no impact. It still took up a good amount of time however and seemed unnecessarily complex and confusing. The two sides didn't really mesh well at all, and though one side was really good, I can't think of the other as anything more than a detriment. The art was solid.