MTL - The Remnants of the Uchiha Are Forced To Save the Ninja World - Chapter 1 second survivor

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.

I returned to Earth as the invincible Knight King. But the Gods came with me.

That lonesome night as he lays dying in the hospital, fearing of death and desiring the taste of life, his mind became unprecedentedly complex with mixed emotions.

Myasthenia gravis — an incurable disease where one’s muscle slowly degenerated until the day when one can no longer move and only tears may flow.

“Is this… dying?”

When he opened his eyes again, he had crossed over into the body of a two months old infant, right in the middle of an assassination attempt.

He was born as the illegitimate son of a noble. His name was Fan Xian; and with that name came the burden of deep political secrets and the legacy of his mother.

He understood; to survive, he needed unparalleled strength, money and political power.

To a new world with the luxury of a new life, so named; Celebrating the Remaining Life.

- Description from Novelupdates

The youngest A-rank adventurer, child prodigy Kaizer, finds three babies who were the only survivor of a destroyed village. Then he decided to give up his job as an adventurer and raise them. Over time, the girls grow brightly and show exceptional talents in fencing, magic and management. However, these girls also seem to love their father, Kaiser!