MTL - Harry Potter and the Secret Treasures - v2 Chapter 1796 I believe

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

Zhang Qiu is an archaeology undergraduate. One month ago, he went to Qinling Mountains with a group of archaeologist doctorate students led by Prof. Fang, to study the newly discovered ancient tomb. While the people were excited to open the tomb, Zhang Qiu was pushed back, and accidentally fell into an opening. Before he fainted, he saw a pair of red eyes staring at him. When woke up, he discovered that he was deflowered! QAQ he remembered the deeds and often dreamed of it.

Twenty years ago, the Gu family’s eldest daughter, Gu Wan, went missing without any news on her whereabouts.

The Gu family was left with only the youngest daughter, Gu Chu, so they doted on her.

Twenty years later, Gu Wan returned. Gu Chu was thrilled and she showed her sister around the city, even giving her everything she treasured.

However, Gu Chu gradually realized that Gu Wan was here to take everything away from her, including her fiance! Their mother said, “We owe Gu Wan all of this. We all do, especially you! Gu Wan only went missing back then because you insisted on having a candy.

That’s why Gu Wan went out and ended up going missing!

She had suffered for twenty years out there! You will never be able to fully repay Gu Wan what you owed her!

Hence, the engagement with the Feng family should be given to Gu Wan!”

Their mother even said, “When we arranged this marriage with the Feng family, although we didn’t specify if it was for Gu Wan or Gu Chu, the elder child should take precedence.

Gu Wan should’ve been the first choice. And now that she’s back, she should take what was rightfully hers. What’s wrong with that?” Gu Chu wanted to defend herself.

She didn’t understand why Gu Wan would lie because she didn’t go missing because of her. Yet, the man chose to marry her sister, and that was when Gu Chu regained her senses.

It was just a man. Men weren’t reliable, so she didn’t want him anymore! Their mother even used their family’s shares to bribe Young Master Feng.

However, Gu Chu was surprised when the quiet and unsmiling Young Master Feng suddenly had a change of personality.

Three times a day, he would propose to her. Gu Chu asked, “Are you in such a hurry to have a wife?” Young Master Feng answered, “I’ve been planning this for a long time. Please bear with me.”

Later on, Gu Chu found out his secret. So he had actually been planning for a long time after all…

One day he suddenly found himself in hell.
All he had was the desire to live and a predation ability.
From the first to the ninth thousand circles of hell, he absorbed dozens, hundreds of thousands of demons.
Even the seven great dukes of hell bowed down before him.

– Why would you wish to go back? Doesn’t his highness have everything that’s in Hell?
– What do I have?

Nothing to eat, nothing to enjoy!
The only things in Hell are the barren lands and terrible demons!

“I’m going back.”

After ten thousand years he returns to Earth.