I Got A Title: Lord Of The Time! - Chapter 98: Is this really a dream?

Xue Xi is forced to fall in love at first sight with this dangerous man on their first meeting. With death being the only other option, she makes the first move:

A girl who calls herself a demon appeared before a timid student named Fumio Kijima. The girl claims to be a campaign girl from the demon world and she gives him the ability to “summon a room” from nothing but thin air.

At first he doesn’t abuse his power and uses it as a convenient ability in his every day life. But one day he is bullied by his classmates under a false pretext and is made to suffer. In the past he would have wallowed in misery and cried himself to sleep, but now he had a power to call upon.

“I will make them regret it!”

Using his powers to summon his “room”, he begins his era of confinement and brainwashing to achieve his goals.

Jin Lin was not an object within the pond; he would transform into a dragon upon meeting the wind and clouds!

Yu Haoran returned to his youth. Not only did he retain all the memories of his past life, but he also obtained omniscient and omniscient domain towers that could accelerate time.

Look at him: Seize opportunities, seize good fortune, destroy enemies, stir up trouble!

This was a story of leveling up and killing monsters.

- Description from Novelupdates

What would you say is the most valuable thing in this world?