Worm (Parahumans #1) - Chapter 184: Arc 17: Migration - Migration 17.1

When an S-class elite assassin-raised captain of a special ops suicide squad comes home from a high-stakes Africa mission, he finds himself offered something that could potentially set him up for life- a curious assignment that he could use to finally exit his days of war and slaughter.

Then placed into a high-school setting, Lin Yi is tasked by the chairman of a top-tier multi-billion company with bodyguard duty for non-other than his own daughter, a certain little Miss of said high-school.

His enemies, once ranging from drug lords, mafia bosses, political figures, and national leaders, are soon replaced with spoiled kids who happen to have rich papas and mamas, and Lin Yi finds his intense expertise and high-threat skillset misused, and very underwhelmed…

But he does get a harem cast as diverse as his old enemies, so Lin Yi decides that, for the sake of messing around with girls as an invincible entity in a down-leveled environment, leaving his bloody and death-filled war days behind is something he’d definitely want to strive for.

- Description from Novelupdates

The frail and sickly Wen Jiexi had always wanted one thing: a healthy body and like a dream come true, one day, she was selected by the system!

System: The amazing me shall grant you a strong physique and divine strength! However, you have to maintain your health through monthly missions! If you fail to complete them~well, then you’ll stay as a female King Kong, forever~

Wen Jiexi: What?! Will I no longer be able to live my life freely again?!!

Mother with an alarmed expression: My frail daughter is actually trying to do the most sit-ups possible?!

Father made a strange face: My delicate daughter ran on the treadmill for an hour?!

Brother’s expression crumbled: Can anyone tell him how his cute little sister who is as precious as a delicate white flower…was actually able to use one punch to break a sandbag and smash a hole through the wall!!!

Through a series of unexpected circumstances, she was pulled into the entertainment industry and became a female martial artist!

Female Fan: Our darling Wen is the most awesome! She’s even more handsome than a man!

Male Fan: The girls today are so domineering! To be able to throw away all of one’s shame, I want that feeling too!

The frozen expression after being hugged by the princess from behind: …..

Wen Jiexi held up a hand: No, no, no! It’s not like that!

- Description from Novelupdates

I’ve reincarnated as the reverse harem game’s villainess, the one and only step-daughter of the Eckart duke family.