shoujo(?) fantasy
2nd year hs students (sophomore? 16-17 years old), 3 classes
2-a, 2-b, 2-c
2 opposing classes (2-a and 2-c), 1 neutral (2-b)

2-a (artillery)
weapon users, ranging from firearms to projectiles without gunpower

2-c (casters)
magic users, black or white magic, both offensive, but can be defensive

2-b (???)
basically the neutral zone, and the police for when it gets too out of hand
melee, basic guns, defensive magic (force fields, shields, etc)

2-3 people from each class are involved, with additional ones who are like "failed chosen ones" who aid them in battle
idk how they're appointed, but i'm thinking like elemental gods and gods of war or w/e idek man jesus or like personified weapons and basically they're chosen based on a certain gene they possess and birth month or something i have no ideA
it happens every few decades and it has been going on since forever, and they're actually tied off
the year is 201x and it's the final battle to determine the true victor
the chosen ones know about th e war the moment they meet any archenemy, it's like innate
in the neutral zone, they'll know once a conflict starts between the two enemies
they're all fated to witness/meet hte others so it's ok
the moment the conflict starts, they're taken to another dimension and shit happens
from there, the true chosen ones get sorted out from the failures
failures are people who can't awaken their power to full extent, but they can still aid their team in battles if need be, except they're far less powerful than the true chosen ones
artillery and casters have an equal number fighters, both true and failed ones
the neutral zone only has 2 officers (the police), sometimes 3 but the 3rd one is really just op and only intervenes when the world is about to explode or something
they fight until the school year is over, and when it is, victories and losses are added together with the ones from previous decades, and then the true victor is decided
the prize is actually full reign on the kingdom in that alternate dimension i guess

but obv since this is a manga there will be plot tweest and spoiler none of them wins something bad happens and they need to ally up and shit wow look at that bromance
i'm thinking something really cliché and having the op neutral person be actually a bad person because they're so op and they're like wow look at my POWER i'll just use it to get what i want ie the reign over the kingdom but no one wants that because wow tyranny
that's all i have rn hm