MTL - My Unrivalled Princess: I Won’t Mess With You - Chapter 413 Used elsewhere

The main character Lei Yu does not have the ability to practice his family’s martial arts. He gets stepped on and tossed around. Due to certain reasons, he leaves the family, coincidentally gains an ability, and makes his own path to becoming an immortal.

- Description from Novelupdates

Once upon a time, a hero had been summoned to a different world in order to defeat the demon king. After the war stretching 3 years ended the commendable hero slew the demon king. And he was forcibly deported back to earth after being dismissed.

Such bullshit!

Elves in addition to beast race, dwarfs and demon race. Even though I wanted to make a harem in the different world I saved! My dream will not come true on earth, where there is no magic at all. Thus, the hero returns on his own. Without the blunder of being extradited to earth this time, he will build a harem of his own in a different world.

After dying a pathetic death as an overworked office drone, I woke up reincarnated as Archer—the bastard prince of the Brutish Empire.My existence is a royal secret as My father, the King, would rather pretend I don't exist. My half siblings get royal treatment while I'm hidden away like a dirty secret.But I have a secret of my own. I was OP.By age two, I realized monsters flee from my stupidly OP mana. By age ten my mana could level cities—if I dare to unleash it.When my half-sister is kidnapped by the demon king, I finally decided to step out of hiding to become the strongest in this new world.

Science and Technology Library: The supreme state of science is theology; an accidental rescue, let Chen Mo get a technology library that collects endless technology, the story begins…

- Description from xbiquge translation