Everything in this world is determined by power level, be it fame, money...etc. And everyone, and I mean anyone, is legible to fight and prove themselves within the "Arena" owned by the "League". 

-And here's a few facts about the league:

-You gain points for winning a match.

-You lose points for losing a match.

-You cannot die within the arena, you simply lose and respawn outside of the arena again.

-You can also lose by being knocked out within the arena.

-You will be permanently banned for any forms of cheating (Except the legend himself).

-You will be permeate banned from boosting or being boosted (Will explain later in actual book). 

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But perhaps the biggest rule, also the greatest unwritten rule is:

Never trust a Yang.

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Power level ranking (From top to bottom):

Challenger (9000+) (300~ members)

Diamond (7000-8999) (1%)

Platinum (5000-6999) (8%)

Gold (3000-4999) (20%)

Silver (1000-2999) (40%)

Bronze (0-1000) (30%)

Water 7 (Literally negative) (?%)

Note: The unranked population of the world are not included.