(Just a note, this is my first review, so apologies if this seems a bit unstructured)

Quick Summary
In a world filled with demons and magic, the people who can utilize said magic are called magicians. Rood, secretly being a strong magician, is sent on an undercover mission to a famous magic school to protect a Duke's son from being bullied. But as Rood involves himself more with the school, it turns out much deeper things are happening with the school, students, and Rood himself.
Thoughts
I really only recommend this series if you need a fun, lighthearted and easy read to take your mind off things. If you are looking for a deep story outta this, go fish, my friend.

Plot/Story
The plot itself is pretty generic. It's executed well, but I never felt like what I was reading was new or inventive. Sure, Rood's big secret in the later chapters is unique I guess, but having seen this same "secret" in other stories really dampened the "surprise". There isn't much to be said on the plot. It's pretty much exactly what you'd expect. There really are no surprising plot twists.

Characters
The characters, like the storyline, are also pretty generic. Aside from Rood and two other characters, most of the side-characters can be explained through common stereotype roles.
Rood however, our main character, is a very bad*** character. The very beginning scenes shows him in his awakened state defeating some pretty big monsters. He could probably actually be compared to Kirito (both in looks and OP-ness) from SAO. When he isn't being his Kirito-esc self, he turns out to be a snarky kid who doesn't take crap from anyone. No one ever expects him to be one of the strongest and most famous magicians, causing for some very funny moments.
Like I said though, other than Rood, the side characters don't have much meat to them.

Drawing Style
The drawing style is a realistic-chibi style. Tall characters but with big heads and large eyes taking up half of their face. Their eyes only get bigger as the series progresses, which I find hilarious.

Black Haze is the very definition of art improvement. I give a solid 10/10 for the current art, which is not what you would expect from reading the very first chapters of the series. The first few chapters, up to about chapter 25, have absolutely terrible art. It's not an exaggeration to say its the worst art I've seen in a manga. However, as the series progresses, so does the art. And it becomes some of the best art I've seen in a manga. So, don't let the drawing style discourage you when you first start the series!

Enjoyment
I personally loved this series. It would have been nice if it were to take itself a bit more seriously and just do away with the comedy overall, but thats just me. I binged the series in a day (no small feat; took 6 hours). I will go to great lengths to find a good secret identity series, and this hit the spot. Though it not be everyone's cup of tea, I do believe everyone will find something in this series.

Overall
Overall, this series was ok. Nothing, other than the insane art improvement, really stood out. It's your generic magician series who struggles to figure out who he really is. I'd give the series a 6/10. You can find better stuff to occupy your time with.