The Girl Raised by the Death God Holds the Sword of Darkness in Her Arms - Volume 2, Prologue: The Isolated Second Army

Haruma Kazuki is a cursed (or maybe just deeply unfortunate) high school student whose lewd, panicked, or absurd thoughts literally manifest in reality — especially when he tries not to think about them. The more he denies or avoids feelings, the more chaotic and trope-heavy the consequences.

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

[You have entered the dungeon at Gwachun Station’s 1st Exit.] When former high school student Kang Woojin finds himself returned back to Earth after being forcibly summoned to a foreign planet for 20 years, he soon finds that Earth is not the same, normal place as he once remembered it to be.