The story is the best point of this series; it's entertaining and leaves you wanting to know whats it's going to happen next and how it's going to end and because of that it's worth watching. Things explained below that are somewhat lackluster is what doesn't make this a great anime but it's still an anime that I think it's worth watching if you want to experience an interesting story.
Character development is not the best but it's there when it needs to be. Is not deep enough to really feel with the character but in this case there is a guy on a mission and all that is related to that that needs to be explained is explained so you can understand why he is doing what he is and why other do to him what they do.
Some stuff might seem odd a bit at first but near the end information is reveled that make the important parts of the plot come together but don't worry is not all like that just some questions that make some stuff seem odd at first but then you understand why it was that way. There might be still things not explained if you go too deep but what really needs to be explained it's explained.
I don't see anything wrong with the art. The only thing that might bother you are the "order's" appearance that is made with 3dcgi which looks bad but compared with other 3dcgi it's ok.
Regarding this anime containing deus ex machina moments: Whatever happens happens in the laws of the fictional world what would be bad would be that the rules they created for the world would be broken by the characters for the convenience of the plot but that's not the case and it's not like some crazy out of the blue stuff happens here IMO. There are some things that are not known that are revealed as you go that save him on the first episodes and then there are ways to use his powers and other's powers that are different than the way they use them at first but it's like you have a spoon and you need to cut food you use the spoon differently to reach your goal. It's nothing that should be shamed as a flaw on any anime IMO.
**micro spoilers**
The only thing that I felt that might come out too much out of the blue was the "fusion" thing but I don't think that it's something so unimaginable or impossible in that world. All the other stuff seems to fall into the rules the anime set for itself like all the fictional works do.
**/micro spoilers**
