Y/n's Harem Academia

Chapter 1: Brain-Jacking Villainess

A cheerful girl with short brown hair, visible pink blushes on her cheeks, large round eyes, and soft pads on her fingertips named Uraraka Ochako was on her way to U.A. High School. The high school that she was currently attending to learn how to be a pro-hero had recently built some dorms for students to live in. Considering recent events, including the villain attack during summer camp and All Might's retirement after fighting a certain terrifying villain, she understood why the school deemed it necessary to build the dorms for the students' safety.

Speaking of safety, Ochako frowned in worry as she thought about her friend, Midoriya Y/n. A boy with bright-green eyes, fluffy dark-green hair, and freckles on his face. The boy had suffered much due to his fight with an infamous villain known as Muscular during the summer camp attack. Her heart could not help but clench at the awful memory of his broken body as he cried in despair due to failing to save Bakugou Katsuki from getting kidnapped by the villains. Although Y/n's injuries had healed and Katsuki had been rescued, she still worried for the boy whom she could not help but... like a lot.

She was so dited by her thoughts that she failed to notice that a small blob of pink slime slipping into her luggage bag...

~At the U.A. Dorms...~

After her homeroom teacher, Aizawa Shouta told her and her classmates about their room arrangements. Ochako immediately went to her room to unpack her belongings. Due to being poor, she did not have much to unpack. However, just as she was opening her luggage bag, the blob of amorphous pink slime which had been hiding inside it suddenly leaped out and covered her face. Too shocked by the sudden attack to even scream, she struggled futilely as the slime started to engulf her face and even probe into her ears. After a few seconds, her weakening struggles stopped entirely as the slime oozed into her head through her ears.

As soon as the last of the slime entered her head, her eyes opened and she wore an uncharacteristic smirk.

???: Finally, I thought I'd never get myself a new host!

Getting up onto her feet and looking over herself, the parasitic being inside Ochako thought to itself.

???: Hmmm... not a bad body to stay in if I have to say so myself.

It then looked into Ochako's memories and thought...

???: And a U.A. High School itself no less. I can make use of this situation!

Uraraka: W-what's going on? Why am I not in control of my own body and why do I have a voice in my head?!" 

Cried real Ochako who was trapped in her mind. The parasitic being made Ochako's body strike a villainous pose as it mentally replied to her.

Brain Jacker: Well, if you must know, I'm what you may call a villainess. You can call me... Brain-Jacker.

Uraraka: You're that slime that jumped out of my bag and onto my face just now!

Brain Jacker: Bingo! I barely survived the Kamino Incident which forced All Might to retire after defeating that monster of a villain. If it wasn't for the fact that I could move around and survive for a few days without a host, I would have been trapped under all that rubble along with my last host."

Uraraka: Y-you won't get away with this! Deku will notice something is wrong with me and...!

Brain Jacker: No, he won't. You see, my quirk, [Parasite Slime], allows me to gain control over any biological woman that I inhabit. Not only I can read your memories to not only mimic your behavior and mannerisms perfectly but even uncover certain secrets about you such as your crush on a certain someone.