It's Actually Not Easy Wanting to be a Supporting Male Lead - Chapter 15 part10

I was proposed to by the Final Boss.

He is a young man without a spirit root. It is believed that this denies him the chance at cultivation. However, a mysterious lady imparts a Supreme Demon Classic to him and from then on, he starts his path of cultivation.
He undergoes a total transformation to emerge as the most fearsome and powerful fiendish demon in his era, that even immortals and fiends are fearful of him, and saints are at his beck and call.
Mastering the Supreme Demon Classic is the turning point in his life. He is able to unleash his immense and divine power from within, illuminating the entire universe!

- Description from Novelupdates

This is a world where technology and the supernatural exist. There are demonic beasts, wars between species, evolution, and danger everywhere. Fortunately, humans aged between 16 to 18 will have the chance to activate certain genes and become gene warriors.

Gene warriors will enter a wonderous World of Origination and begin their adventure there. They will seek treasure and copy extraordinary genes to gain wondrous strength, becoming the main power against danger.

Lu Yuan transmigrated to this world, bringing with him a cube that can evolve genes without limits.

I woke up with a start.

I have transmigrated, am handsome, and have the golden touch. I am going to win at this! Am I going to be the protagonist?!

I, Lu Yuan, am definitely going to become the pillar of the human race!

Roy’s life was nothing special. The only thing commendable was the last few moments when he saved a mother and her child from a drunk driver.
…
It’s really an egg! Damn it, what kind of monster have I become? Did I fall into Hell instead of making it to Heaven??
Join Roy as he ventures through various worlds with the Custom Made Demon King System—a system that allows Roy to draw anything he can imagine and create it through exchanging souls!