I Gave Up Being Stronger - Chapter 14

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 million years ago, he had traversed the Nine Heavens and Ten Earths, braving countless mysterious Life Prohibition Zones, in search of a way to resurrect that foolish woman, but inadvertently learned one earth-shattering secret after another. Thereafter, he went through nine cycles of reincarnation, strategizing over the world, casting his net across the heavens, with the Myriad Realms as his board! In this life, he had returned from reincarnation, his Qi engulfing mountains and rivers, “It’s time to close the net...”

Maid, older sister, younger sister, and even mother, all of them.