The Simple Life of Killing Demons - Chapter 27Book 12:

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

Liam feels increasingly suffocated by debt, paralyzing shyness, and the monotony of everyday life. However, everything falls apart when he is falsely accused of a crime and is on the verge of being expelled from university. But as he's wandering hopelessly back home, a strange voice echoes in his head, informing him that he has received the “Harem App.”Suddenly, his life is turned upside down, and he now has supernatural powers to win over beautiful women. At the same time, he finds himself entangled in conflicts far beyond those of a mere human.