Great plot and well-built characters. One thing that could be improved is maybe the "bad side" of the main character, it seems he is some godly good person and destroys the bad guys one by one. Things seem a bit too simple if you ask me although there is the one demon-king that seems unbeatable for now. It would be nice to see a bit of the difficulties the main character can be facing, since each time a hurdle arrives, he deals with it in a few moves.
Although it is not part of the genre necessarily, it seems the main character could have some kind of romance going on as well. However, I do like the fact that the authors alternated between men and women on side characters. Maybe some fantastic characters are to be coming soon?
The fights and level aspects of the story are well drawn and established. This make the story all the more entertaining. I am excited to hear more about the second volume/book.