I'm Alone In This Apocalypse Vault With 14 Girls? - Chapter 63 - 12.1: The Cousin

Entering the mortal world for a hundred generations, do not compete for the youth of one life, but only for the day and night of a hundred generations.

Seeking immortals in the world of mortals.

My name is Li Qing. I have escaped from the mortal world in the third life, entered the Tao in the ninth life, and become immortal in the hundredth life.

(longevity stream, non-simulator, non-reincarnation rebirth)

(Bai Shi Shou Yuan, One Life Life)

- Description from novelbuddy

Char lived alone in the closed beta test of “Fantasy World” for thousands of years. He had already experienced 177 data wipes. In this span of time, he had already successfully charmed all of the NPC beauties, challenged all of the bosses single-handedly, gathered all of the divine weapons and used hundreds of methods to complete the online game as though it was a replayable console game. Just as he was losing the ability to differentiate whether he was a player or an NPC, the public beta started for “Fantasy World”. As such, a player who was even more terrifying than a boss was born.

Lin Yun's life is in shambles. As a widowed single father, he's struggling to connect with his teenage daughter, facing a midlife crisis, and battling a painful shoulder condition.But when he discovers his daughter is a magical girl - fighting monsters and saving the city in secret - he's forced to confront a whole new set of challenges.As he grapples with the dangers of her secret life, Lin Yun must also confront his own purpose and what truly matters to him.Will he be able to support his daughter while finding his own way forward in this heartwarming tale of family, love, and self-discovery?

Another entry in what you can call the Proto Harem Series: the books written before the Harem Series that take place in the same world.

It’s about a swordswoman whose student is captured, so she goes to rescue her.