Plot/Story
"We will save then world, then we'll destroy it." A MUST READ FOR ANYONE AND EVERYONE ;the basic premise which in my opinion alone is a breath of fresh air, but with such wonderful execution makes this manga a unique gem hidden, like a needle in a haystack.

Basics of what's going on :save the world then destroy it XD. It starts slow and blooms beautifully, although it isn't the most glorious manga out there and is subject to some cliches and genericness, altogether the story will keep you spell bound once it gets rolling and will juxtapose great fights, heartwarming moments, teary moments, genuine laugh out loud moments, bits of tragedy and a dose of romance.

It's not perfect yet in the sum of it's parts it's definitely in my opinion fantastic and at the minimum worth a shot. Also wonderful is the weaving of greater themes of trust, the nature of people, believing in yourself, coming of age and maturity. As I read in someone else's comment don't let the tragedy tag upset you. There's less tragedy in this than Full Metal Alchemist.

Characters
The characters of this series are well varied, colorful. The primary traits the cast left on me were strong, realistic, wholesome, wacky eccentric.. Although the situation and setting gives them a larger than life role to play they still feel relatable. They're nothing more than a variety of everyday folks you could find anywhere in the world. Some lived their lives mired in tragedy, some not. The author presents them (most of them) well enough as ordinary people but they are far, far, far from being boring. They truly feel like nothing more than ordinary people put into an exceptional situation.

There's also some awesome character development for some of them.

Drawing Style
Drawing style isn't special or fantastic but each character looks distinct and can be told apart from the other.

Enjoyment
An incredibly enjoyable manga, haven't been so moved by a manga in about a year and was glad to have this break that drought despite the fact I'm sad about it being over.

Overall

This manga will easily sit in one of my favorite series of all time, the real tragedy is that this series isn't very well known. I haven't been so spell bound by a simple and elegant package. I haven't enjoyed any series blending such absolutely wonderful characters, a different goal/conflict, humor and good character development. It takes all these different little elements that make a good story and mashes them together.