It's Not Easy to Be a Man After Travelling to the Future (WN) - Chapter 9: Gene Stimulating Agent!

Alternate Title: Kumo Desu Ga, Nani Ka? - Game SystemElliot? Yeah, he got isekai'd. Bam! Straight into the world of “So I'm a Spider, So What?”. And guess what? He wasn't some puny human or, well, a spider. Nope, he lucked out and got reborn as a freakin' Earth Dragon!But wait, it gets better. Ding! He awakened the 'XX Worlds Game System'. You know what that means? Skills! Skills from all sorts of crazy games!And the kicker? His new neighbor in the sprawling Great Elroe Labyrinth was none other than the little spider gal herself, Kumoko!So, what happens when two totally broken characters end up living next door to each other? They team up, duh! Their genius plan? Hit all the poor monsters in the Labyrinth with a two-pronged attack! A good ol' fashioned sandwich maneuver!But Elliot had a little secret. “Heh, sorry folks,” he probably smirked to himself, “but your boy Elliot here? He's playing with cheats activated!”Skill Acquired! [True Man's Slash]!Skill Acquired! [Skull Splitter]!Skill Acquired! [Planetary Devastation]!

Lin Jie, a transmigrator, is the owner of a bookstore in another world.

“A cheat system? Do you take me for a fool? Nowadays, where can you find such a good thing falling into your lap? Scram from my head. Is this is new kind of fraud? Or is this a murderer training system of aliens that contains the ability of hypnotism?”

“No, I am the chaos that whispers from nothingness, the nightmare of all living beings in the Southern Ten Stars, the successor of the unparalleled God and… your elder sister.”

“…I only have a younger sister, I don’t have an elder sister!”

“No, you have one. I am an illegitimate daughter. It’s just that your dad didn’t inform you.”

- Description from Novelupdates

My old man pointed to the flower-like woman and said, "Call her mother from now on." He then pointed to a flower-bud-like girl and said, "This is your little sister."