In Different World with Naruto System (WN) - Chapter 288: Trace Discovered

Doomsday comes, and human beings enter the heavenly world.
Ten years later, Yang Chen, who was betrayed tragically, returned strongly with the Tianyu bug. In this life, he vowed to make the betrayal pay the price. He has a powerful bug bonus, just like an open hang. Frightened to hear…

- Description from novelbuddy

Instead of causing chaos with my knowledge of the original work, I assisted the protagonist.

I successfully completed the story and now planned to retire and live peacefully.

However, it seems the protagonist still needs my help.

An academy professor? That’s nothing much.

But why is the state of the academy so strange?”

Awakening to a post-apocalyptic world infested with zombies and mutated monsters, Alex makes a startling discovery: he possesses a system that grants him access to unlimited resources every day.【Congratulations, you've received unlimited bottled water.】【Congratulations, you've received unlimited 9mm bullets.】【Congratulations, you've received unlimited cold medicine.】...With each system notification, Alex's chances of survival soar while others struggle to stay alive.As everyone else fights for their lives, Alex finds himself living in luxury, residing in a lavish mansion where he leisurely sips red wine and savors grilled delicacies amidst the chaos of the end times...

Among the demons, the supreme ones are called “Great Saints.”

A young man leaves his mountain village and travels around the world. By unceasing efforts, he finally becomes a legend of the age.

- Description from Novelupdates