Oh man! Truly amazing artwork!
Even though you say you are an amateur... it looks pro to me
Next, just my ideas on the setting and some general stuff. Don't take too seriously
However... I believe you have way too much stuff going on. First, the genre list is too broad. And i would decide between shounen or seinen. Pick either one, but not both. Also, i'm not certain about the horror you've picked. Is it something that really suits this manga?
For example: Fantasy, supernatural, mystery, comedy, shounen, action, adventure.
Or: Fantasy, supernatural, mystery, comedy, drama, seinen, action, tragedy.
I would leave tragedy and drama out from the shounen, and adventure out from the seinen (this doesn't mean that the story can't have any of those, just not focused on). It makes a bit more clear frame to work with. Also... horror is a bit iffy in my opinion unless you really plan on making this a horror. In that case, i would still remodel the genre list a bit.
Synopsis has a similar problem. It is way too detailed in this point. It's a bit of a mess, as there's so much happening in there. HOWEVER, don't get me wrong. It's absolutely crucial that you've planned out so much already. You always need more lore and background to be able to fit something within the premise so that the story itself doesn't suffer from it (i.e. it's a credible world with convincing characters).
My example of your synopsis (i would keep it simple): The First Angel of Penalty has rebelled against God. Wisely, a boy with an unknown past is found homeless in Labunagaan by a Black Guardian, a Reaper, an unknown creature, which resides inside Wisely and who hates humans. At the Selection Day Wisely is chosen by two Black Guardians, and he enters the magic school situated in the Sacred Land. After entering the school strange things start occuring. Students start to disappear and Wisely discovers the cruel truth bit by bit of which the humans are unable to see. Is there a mastermind behind all the incidents which keep happening within the school ground?
This is probably totally different what you've imagined, but the point is to keep it simple
. All the tournaments and journeys into the magical world would happen later.. which would be covered by the manga itself.
Everything else is not needed. It will come clear when the story unfolds. And it will keep things interesting to find more stuff later on, as the reader learns more about the lore and continues with the story. Backgrounds can also be explained later.
Your characters feel interesting enough.
My first impressions is that Wisely is like Spike from Cowboy Bebob except that Wisely hates women and has a short temper. He seems a bit cold. Though no doubt a very cool character. Have you thought of making him a bit funny as well? I would expect witty and sarcastic humor from him.
Rynart is a bit more interesting. He is like Ishida from Bleach + Yozora from Boku wa Tomodachi ga Sukunai personality wise. However you describe him to quickly back off in a bad situation. Is he a bit of a scaredy cat? Or is it more of an instinct thing? This makes him a bit conflicting in my opinion, but he sounds interesting. I would also expect some funniness from him as well. More like trying to hold Wisely back in crazy situations.
Also the Prince of Labunagaan is a bit weird, as he is quite the joker, badmouth (extroverted) but also shy and afraid of things (introverted). He might be a bit too complex of a character. But this is just how i feel about him. Maybe he will turn out different ^^.
The Angel of Penalty is a solid character. He seems really cool and would be perfect for a shounen manga.
So there you go, some of my ideas about your work. Don't take everything too seriously as i said. Just my opinions. ^^