Jujutsu Kaisen: I Can Travel Back in Time - Chapter 29 - 23 : Sweet Disasters

A supreme expert in the Immortal World had died, and a strand of his soul returned to its original body on Earth. Tang Xiu discovered with amazement that ten thousand years passed in the Immortal World, yet only a single year passed on Earth.

Ruthlessly betrayed by his lover and trusted friends, Tang Xiu found that his soul went back to his previous body on Earth, and, despite he spent 10,000 years in the Immortal World, just a year has passed on Earth and many things have changed. Having an unsurpassed knowledge, Tang Xiu will protect his loved ones and go back to the Immortal World to take his revenge.

- Description from Novelupdates

Dynasties rise and dynasties fall, like the tide washing the sand.

Noah was a nobleman. An orphan.Born with an empty constitution, he was pretty much useless…Until he realises the World’s Greatest Secret.The verse they were living in—It was a freakin fantasy novel.And the worst part?He was supposed to be the villain.***“Hehehe— So what? I just have to substitute someone in my place…Yes!”“All I have to do is to hire a Villain.”