The premise of a special boy who is the target of every bad guy out there who learns of his own powers and develops them at a magical school with friends, with all kinds of cool monsters and abilities is a good one. It's cliche shounen, but it usually works. And it works well here. The action shines, and his inner conflict of his capabilities and his limits seem very believable. Add in ambiguous villains with seemingly relateable traits (Satan is obviously the main villain, but I'm talking about the others), and you have a good complex action theme going on here.
The main problem that I have is that with such a diverse cast, the characters seem to be lacking something. For example, I think that a manga like this should not only focus on the development of his powers, but the development of him as a person. What does that mean for me? It means there are good opportunities a romance angle in the story. The main female protagonist is too soft and clueless, and although a valued secondary character who admires our hero from afar, she is not a strong enough character to carry on the role of a heroine. There seems to be a tsundere but her personality is still quite annoying and she lacks the charm or the good character design to pull it off.
The other problem I have is that his peer, his brother, was all of a sudden his authority. This is quite disconcerting to me. And he doesn't teach his brother anything. The main character goes off and does what he wants and gets the proper result. So what is the point of a mentor? And the fact that he treads the line from mentor to peer is not good UNLESS the common point between the two is a point of comic relief. I don't like how serious he is, yet his advice seems to be useless... he seems to be on a ivory tower and should be inaccessible yet he is his younger brother... also the fact that if you see his character design in the 1st chapter and like.. the 5th chapter he obviously aged around 6 years. It's clear the author did not intend for him to be an authority figure, and the hurriedness of that connection shows its inherent flaws.
It has good action and a good premise for an interesting development of the fantasy world - for example, I love the architecture in this manga. It's something out of final fantasy, 18th century japan, modern day japan, and harry potter. However, ultimately I find that the main problem is that I can't love the manga because of its flaws in its cast. There are opportunities to explore both magic and fantasy and development within the school life role a la mx0, but in this aspect the manga is lacking.
However, if you just care about action and shounen elements, this is a great manga.