MTL - Forty Millenniums of Cultivation - ~ Fish girl six kills

It is the story of a young man who died and was reborn as a level 1 skeleton soldier in an underground world. Follow our protagonist as he struggles to survive in a foreign, RPG-like setting surrounded by danger and monsters. Watch as he levels up and overcomes all obstacles through sheer perseverance and wit, rising to prominence

What should I do if I cross to another world and become an NPC?

This idea has been deeply rooted and sprouted in William’s mind!

Therefore, he decided:

I want to be the strongest NPC in history.

Wear the thickest armour and give the most vicious beatings!

Who says an NPC will be killed by players?

Who says an NPC upgrades more slowly than players?

Who says an NPC must explode equipment, I can explode in more ways… Bah humph.

Anyway, it’s impossible for me to die. Just take a look at all you trash players. Your father will stand here and let you chop for an hour without a frown!

- Description from Novelupdates

This is a story about the protagonist getting the system, going crazy in the biochemical apocalypse, producing aircraft and tanks, destroying zombies, saving good people and killing bad people.

- Description from novelbuddy