Isn't that the exact same thing as in solo leveling? A disease that makes you sleep more and more until you never wake up?
There is a lot of similarities, heck, the name alone, Level up Alone compared to Solo Leveling/Only I Level Up.
But it is still different. Guns are still effective, the powerup is not just combat related and generally the world seems more grounded. It still has the gamelike elements, but there isn't the loot drops.
I prefer the feel of this, but yeah, definitely has taken inspiration.