Genius Sword Immortal (Feng Yin Zi Chen) - Chapter 293: Rejuvenation!

A man is reborn into the world of Avatar: The Last Air Bender as a waterbender from Katara's tribe. Best of all, he was the same age as her, and he had a system with him to help.He knows the future and a system that lets him continuously get stronger by completing quests or long-term missions, as well as giving him the ability to copy abilities from others for himself. He will become invincible in the world of Avatar, even more so than the Avatar himself.

500 years ago, Chen Xi was devoured by a crack in the void and was transported into a cultivation world.

500 years later, he returned back to Earth after enduring through several hardships and discovered that only 5 years had gone by.

…

In the courtyard, beauty at the side, a candle flame wavering.

A gush of clear wind, half a full moon, the peach tree remains unchanging.

…

Wait, whose kid is this?! Why is she calling me papa? Gazing at the little girl in front of him with skin as pale as jade, Chen Xi froze.

…

　
Returning home from cultivation, starting as a stay-at-home dad.

In this life, not fighting to be a king nor claiming to be a tyrant, only praying to peacefully be a wife-pampering mad devil and a child-protecting daddy!

- Description from Novelupdates

It was a time where demons roamed the earth and chaos reigned. The story took place in Luoyang, the legendary capital of the times. During the night, one could find people holding on to their food with dear lives as they faced off against stray dogs, people with weapons in hand vowing to fight against Fate to their very last breath. There was bloodshed everywhere as some died meaningless deaths, while the strong tyrannized the weak and the truth was frequently hidden. Some of the citizens had completely lost their mind, while some died on their travels. Most importantly, the words of a certain youth caused much panic in the human world. It was a time of little warmth as nights in the capital were frequently accompanied by gusts of wind and rain, and it would be covered with snow during winter. Such were the days…

- Description from Novelupdates