SSS Awakening: I Can Class Change at will

Apocalypse descended, and humans were given a game-like system to defend themselves. At the age of 18, every teenager underwent an awakening ceremony—a chance to gain a class and access the First Sanctuary, where lives became currency and power was earned through blood.

Moon appeared to be a failure. Branded as a Null during his awakening ceremony, he was abandoned by his girlfriend and cast aside by society as worthless and powerless.
But fate had other plans. Moon awakened not one, but two unprecedented abilities that defied the world's understanding.
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[Talent: Grim Reaper - Gain 5x lives from every kill]
[Class: Classless - Whilst everyone is tied to a class from their birth, you are free from the restrictions of the system. You are able to learn any skill from any class based on your comprehension or from fruitful encounters.]
......
With the power to master any class and a talent that turned every kill into exponential strength, Moon set out from the bottom to prove the world wrong.
In the First Sanctuary, where only the strongest survive, Moon would carve his path with blood and determination. Ascending from a worthless null to an existence beyond legend.