80 years ago on earth.
It was a peaceful day and everyone were working perfectly until a meteor crashed in an island near Indian ocean and mutant creatures started coming out of oceans of all countries
At the same time some people who were alive got powers by specific stones that were changed from normal stones by radio active impact of meteor.
Among people with powers. There were many people with high power and high class. People got abilities of healer, wizard, swordsman, etc.
Their class and abilities determined by the stone they used.
Red- Epic tier
Yellow- High tier
Blue- Medium tier
Green- Low tier
Intelligence of mutant creatures became high after years and year and they also captured some parts of land in ground.
To fight them heros united and made guilds to protect their land.
At later government started ranking system in heros and guilds. And started to giving them salary in millions.
Ranking system
SSS-class
SS-class
S-class
A-class
B-class
C-class
D-class
E-class
Mutant creatures also started getting rank
Destructive - class
Epidemic - class
Disaster - class
Normal - class
Now from here journey of our hero starts to take parts of earth conquered by mutants back.