Guardians of The Damned - Chapter 20: Necessary

A skilled but unfortunate modern-day assassin was killed in a freak accident. However, he soon found himself summoned to another world by an evil wizard, who had him possess the body of a boy as an experiment. After successfully planning the evil wizard’s downfall, he used the wizard’s body as a springboard to gain influence and power in his new world.

- Description from Novelupdates

Liu Yan, an ordinary office worker from Earth, unexpectedly traveled to a strange world.

The heroes of the ages are on the side, embarking on a journey to conquer the heavens.

- Description from novelbuddy

Jinhyuk, a gaming Nutuber, was the only person who saw the ending of the game [Tower of Trials].

However, when the game’s popularity declined, it became difficult for him to continue making a living as a gaming Nutuber.

Since he already saw the ending of the game, he was about to quit playing. But that day, [Tower of Trials] became reality, and Jinhyuk, who knew about every single thing in the game, took over everything faster than anyone possibly could! “I’ll show you what a true pro is like.”

Li Ke Lin (also Li Colin), a Chinese office worker, woke up to find himself suddenly no longer Li Ke Lin but instead Colin Lee, son of multi-billionaire in America. Having taken over the body of Colin Lee and carefully imitated his manners and bearings, his next goal is to inherit his father’s wealth. However, when his father lists the condition of marrying a woman who feels repulsed by Colin Lee’s (not Li Colin’s) dalliances, and whose very nature is the complete opposite of Colin Lee (not Li Colin), what must he do to gain her affection?!