Kage was not ready for human school.
He was technically joining three weeks after the first day
As he is sharing the same class schedule with Mira, he just follows her around.
In Kage's class he learned that...
The Gates first starting to appear 57 years ago. These gates unleash Creatures that modern weapons had no effect on. This was around the same time people around the age 7-25 started to awaken powers to fight off these creatures. The creature they kill sometime drop artifacts, which could a weapon, amour, or a unity item all with different abilities.
After a while a group dare devils of teenagers enter one of the gates. They were able to return one day and the news they brought back change the world.
They said were transported to a different world. They spawned in an ancient city that was flood with creatures. They fought through the creatures and reach a strange red gate way that is much different that the gray gate that appear in our world.
When they went through, they return to our world, once back they realize they were stronger, faster, and gain two new ability, one ability was to travel back to them imprint left behind in the world and the other was something to do with their bloodline ability.
The government soon created a watch that connects with you via your blood, that allows you to check, your rank, class, artifacts, abilities, your bloodline rank and energy levels.
After that the government create schools like this one to help prepare kids for their first gate entry. Your first gate entry sends you to a wrong place in the other realm. By holding hands with your groups makes you all get send to the same location.
The system rank goes like this
Base - a newly awaken
Enhanced- absorb gate cores
Advanced- absorb enough Gate cores
Superior Absorb enough high-level Gate cores
Apex- face the first Trial
Mythic-face The Secord trial
Absolute- no one has an idea yet
The class is based off your blessing you gain form a god.
(Authors note: Gate creature has the same ranking system, but Class is a different for them)