The orginal world of this story is th earth, in 2057.
The power system is simple
ther ehis awakened first:
The awakened are people who have mana and a job, for exampl assassin, warrior or mage but there are also spesifict job like elemental mage, shadow assassin, or hero
They can get skill related to their class with trainning and can upgraded them trought mastery
Then we have donjon, donjon are portal who lead a way throught another realm, awakened need to go in this donjon to lvl up.
exampl: E rank awakened go in a E-rank donjon, then he finish and escape from it, he will come back as a D-rank same for every rank
Then who have wave, wave are a group a monster who attack human group, village or even city, they also can have rank determined of who is the leader.
Awakened can fell the mana of the leader and tell if it's an S-rank wave or a F-rank.