MTL - I Let the Boss A Become O - Chapter 34 ·?

When she wandered the border of life and death at the age of three, Cordelia realized that she had been reincarnated into a game she had used to play as a high handed noble girl. A dark future would await her if she fell in love with the Prince. Therefore, for the sake of a normal life, there was no road but to avoid the powerful prince and the heroine…… But just doing that would be boring. She finally was blessed with a beautiful appearance so she resolved to polish herself, firstly by beginning to study herbology…… This is that kind of story.

“With my knowledge, give me a fulcrum on which to place it and I shall move the world!”

…

Sorcerer Continent—a world where sorcerers exist. Wielders of arcane knowledge. Masters of all elements. Sovereigns of space and time. These sorcerers governed the world with their unrivalled prowess. One day, a young man awakened into this world with his past forgotten and no place to call home. Follow along as Glenn, by relying on his luck and wit, tries to survive and advance in this unforgiving world. Entangled within the machinations of fate, political schemes, power struggles and wars, he forges his own path and creates a place for himself.

- Description from Novelupdates

Humans across the world ended up joining a “Demon Kings and Heroes game”.

Several billion people were set down upon another world to act as “Demon Kings” and “Heroes”. Everyone has to chose their starting races from the start.

Zhang Nu was set in the Demon King camp.

He discovered that he could see hidden information that no one else could.
[Slime Demon King]. Low grade demon king bloodline… Not recommended!
[Kobold Demon King]. Low grade demon king bloodline… Not recommended!
[Dark Elf Demon King]. Mid grade demon king bloodline… Can be selected!
[Bloody Giant Demon King]. High grade demon king bloodline… Recommended!
[Abyssal Dragon Demon King]. Strongest starting bloodline… Extremely recommended!

The strongest Demon Lord dies, and reincarnates as a human. Not only that, he because of various incidents turns into the hero’s best friend.

Follow his journey as he tries to help the hero escape his fate, and on the sideline to conquer the continent while he’s at it.