Warlock of War: My Ares System - Chapter 2 System?

In short: an old lover gave me a little piglet.

Qin Zhuopu, a workaholic, has been single for many years. As he reaches middle age, his family is desperate for a child.

Until one day…

“Mr. Qin, your son is already in primary school!”

“???” I have only had one boyfriend!

Seven years after the breakup, the old lover returned to the wealthy family with a little fat pig in his arms: “Zaizai is a big eater, I can’t feed him. Zaizai’s primary school homework is too difficult, I can’t do it. I’ll give you guardianship from now on! Will you let me go to your construction site to move bricks? Son, say ‘Mommy’!”

Mr. Qin: (No, I couldn’t give birth to such a fat kid!)

Later…

Onlookers: I heard that Mr. Qin has adopted an illegitimate child born to his old lover by some woman?

Mr. Qin: Let me introduce to you, this is my own cub!

- Description from Novelupdates

He was on his way to buy some beer to celebrate his acceptance as a civil servant when he was suddenly isekai’d by truck-kun.

“How long has it been?”10,000,000 Years, a period of time which he dwelled in the endless abyss as a captive of war.After his fall, he lost everything to the hands of those who stand above the heavens.The twelve gods of the constellations, the Primal Zodiacs!Creatures who descended down from the absolute light to consume all.He fought against them only to fall prey to their destruction, locked away in the endless Abyss.Astroth Vermont lost it all, his will, his empire, his powers and his mind, all he knew was despair.But that’s until he woke up, Returning back to the world as someone else.The Blackest Evil was reincarnated as the Tenth Young Master of the Reinhart Family.His return is going to shape the world, returning all into chaos!Will he exact his revenge?Who knows, welcome to the land of carnage

As a promise, he went out into the world as an assassin. 3 years later, after becoming the Supreme Assassin, he gave up on everything he had and returned to the ranks of ordinary people. But one day, Kismet, a mystical game created by the National Research and Development had appeared.

Enigmatic hands, spectral frame, and one cunning strike just like the swing of the Grim Reaper. The Supreme Assassin takes on the mystical world, and how his legendary tales sets off, progressively ascending the altar to becoming the best.

- Description from Novelupdates