I Became a God in a Horror Game (Unlimited) - Chapter 115.2: Love Welfare Institute

In the early world of immortal cultivation, there was no physical cultivation among immortal cultivators. And a top bodybuilder who came from the earth has opened up a new path here and became the ancestor of physical training.

- Description from novelbuddy

Upon being reborn, she immediately offends a vicious two-faced bigwig.

Xiao Rou, a girl growing up in a poor countryside family, finds that she’s actually the daughter of a wealthy couple. Her mother had mistaken another girl for her back at the hospital. Thinking she would change from an ugly duckling to a noble swan and live happily ever after with her real family, reality strikes her in the face.

There’s the so called class transfer.

Among the high school students that were given cheat abilities, Kirishima Ran was given 『Underling Training』for some reason, a skill that can make a woman a slave.

Ran who was driven out by the kingdom using an absurd reason will make use of the given skill freely to take revenge on his classmates, release his desires (This is mainly the reason), and fight off the world’s system.

It’s a story of him using his wonderful skill making his classmates turn to an obedient cute and lewd slave.