From a story standpoint the anime is very interesting as it is a typical shounen story with a very interesting and new premise . The MAL synopsis does a good work of explaining it so i wont get into the details. The problem lies in the execution of the story. Writer does a pretty good work of building the world and give us few interesting power and characters but the way we are given that information is not creative at all. most of them are just exposition dumps where people just tell each other stuff which sometimes feel simply stupid and lazy writing at the best. But regardless the story itself is interesting so it keeps the person watching engaged and makes them feel to get to know the world our characters lives in more.
Now the art and animations for this anime is really good ,top-notch. It is handled by David production, which is a well known studio but this in by far their best animated anime. That really did amazing work with action scenes which are loaded with intensity and fluidity ,it's animation and character art is it strongest point.
Music was decent ,it was not a masterpiece but not bad by any means. The background music for characters and action scene was mostly done right and is in the sync with what is being shown on the screen. It complements it's amazing animation quality very well.
Characters are it's weakest point , it is what makes this anime drags infact . With such a interesting premise and overall plot for the story the character development is the worst and done very badly. Their are few interesting characters but most of the characters we spend our time whit our just plain and their backstory is just thrown at us . The female characters are just here for fan services and have no purpose in story ,the fan service is so much infact that it just seems a cheap move from writers part to keep viewer engaged but in reality does the opposite.
The anime is overall good enough for a person to be invested by the story but might be eyesore for people looking for good character development.
