I've got a Succubus for a Girlfriend - Chapter 18: Exploration

Crimson Vale Academy—where reputation is currency, and failure is a stain you wear on your sleeve.Behind gothic walls and spotless uniforms, students aren't just educated—they're measured, ranked, and pitted against each other in a brutal meritocracy. Privileges are earned, not given. The strong rise. The weak vanish.Enter Kairon Vale, a transfer student marked Rank D—the bottom of the bottom. No badge. Just a stitched black fang, branding him as “Obsidian”—a warning to others.In a system where points dictate your value, Obsidian-ranked students claw for every opportunity to ascend into the prestigious Golden or Platinum ranks—where comfort, power, and influence await. But for most, it’s a losing battle.Yet Kairon isn’t here to fit in, impress, or play by their rules. Cold, calculating, and impossible to read, he watches the system… and waits. Because while the academy judges worth by numbers and names—he understands something deeper:Everyone wears a mask. And every mask can be cracked.Let the games begin.

“From today onward, you’ll take your brother’s place and take over the inheritance of the Gu family!” With her mother’s declaration, she became her twin brother’s substitute.

Dressed as a man, but unwittingly enticed a lot of sisters!

Incidentally, she also captivated the younger sister of the most powerful authority in China, shouting to marry her!

Ming Shao was furious: “From now on, you will follow me. I will train you to be a qualified brother-in-law!”

Since then, she eats with Ming Shao during the day and lives with Ming Shao at night.

She has always thought that Ming Shao treats her as a prospect brother-in-law, but one day, Ming Shao pushed her down the bed and plundered her mouth!

Hey! Didn’t he say he wants her to be his brother-in-law, how come he turned into her boyfriend?

- Description from Novelupdates

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.