Game of Thrones: Knight's Honor - Chapter 281: Return to Summerhall

Kang Min-hyuk, the loser of the checkpoint, gained a high-level magical civilization and everything changed.

On modern-day Earth, An Lin seems to have been abandoned by God.
When his father suddenly disappears, An Lin is left with his father’s immense debt, putting his life at risk.
After being forced to a rooftop by his pursuing creditors, An Lin is unexpectedly swept off his feet and brought to the ground safely.

After learning that he was saved by an Immortal, An Lin is gifted, seemingly out of pure generosity, the ‘God Of War System,’ and a pass to a new realm.
Follow An Lin as he experiences a whole new world of legends, meets many new friends, acquires legendary weapons and tools, and starts on his path of becoming a powerful cultivator. There is never a dull time in An Lin’s new life with his ‘great’ new system!

- Description from Novelupdates

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.

A world where awakened individuals with special powers emerge due to a system. At the New Spring Kindergarten infant class, Gru awakens as an S-rank Hunter at the age of 4. Along with this, there is a quest assigned to her… [Quest: A child needs a strong guardian!] Why is a guardian needed? That is because Gru has no mother or father. Gru, who had no family, is adopted by the greatest Hunter in South Korea after many twists and turns, and along with that, new skills are developed… [Let’s try registering a new guardian in the slot!] [Children can earn ‘filial piety points’ through various activities, which can be used in different areas.] Gathering guardians enables faster growth? ‘That’s amazing!’ Alright, I’ll gather all the S-rank guardians!