Koro Sensei's daughter (Assassination classroom x Oc)

Prologue

A woman who was holding a small child who looked to be around one and asleep, walked down a hallway and stopped in front of a door.
I'm sorry but it's for your own good the woman thought to herself then knocked on the door and ran.

A man with black hair and gray eyes opened the door, and saw the little girl.
Why is there a kid? Where the hell is their parents? The man thought to himself looking up and down the hallway of the apartment building, then looked back at the kid. Damit I may be an assassin but I can't just leave a kid to die especially in the world this is. He thought then took the kid inside the apartment.

Over the next 3 years he took care of the girl then started to teach her to be an assassin along with his other protege. He often used fear as a method to keep them in line but it was just with intimidation and not violence. The girls name was Koroshiya which means "Killer" in English, her real last name was Yanagisawa, and Yukimura, but she used the name Korogane instead. The man who took her in was called The Reaper as he didn't want to share his real name, Koroshiya would call him by name most of the time but thought of him as a father and would sometimes slip up saying it.

On the outside she was normal but she had a secret only The Reaper knew of she had tentacles that grew off her neck, she had for as long as she could remember. One day when she was 10 the tentacles asked her what she wanted to be, she said nothing she wanted to live her life by her own means. She would wear a special scarf that she had when The Reaper first took her in to keep the tentacles from going berserk when she turned 12 she was able to control the tentacles and hide them without as much pain as it would usually be. She had to keep them secret if she didn't her and The Reaper feared she would be hunted because of it.

One day when Koroshiya was 13 almost 14, Reaper and his Protege were out on an assignment, while Koroshiya was in charge of the apartment. There was a knock at the door.
Koroshiya grabbed her gun and held it behind her back while going to answer the door, "Can I help you?"
"I'm here with the ministry of defense we believe that the assassin known as the Reaper lives here," The woman at the door said.
"And why exactly do you think that," Koroshiya said keeping her composure while tightening the grip on her gun.
"Someone claiming to be his student said he lived here," The woman responded.
Koroshiya pulled out the gun and shouted, "What the hell do want with us and why did he tell you?"

Koroshiya was detained and taken into custody. Since she was still a minor the Ministry of Defense decided to try and "rehabilitate" her since they knew she was being trained to be an assassin.

Koroshiya would be taken to a training that was taught be none other than Akria Takaoka since everyone thought he was the best man for the job. This resulted in many beatings by Takaoka for "disobeying". She was never able to escape because she was being tracked by a tracker they implanted on her arm, and couldn't retaliate because of her bloodlust taking over. This went on for around a month.

They put Koroshiya under the custody of some rich guy who worked for the place.

One night she got back to the place she was staying at. The back of her shirt was all bloody from Takaoka, she had a bruise on her cheek, and had a limp. She heard a gunshot from upstairs and took out her survival knife.
A blonde woman with a very low cut shirt came down the stairs and saw Koroshiya.
"Who are you?" Koroshiya asked in a weak tone.
"Kid are you ok you're bleeding," The woman asked.
"I'm . . . Fine," Koroshiya said her words were slurred then fell from exhaustion.

Around an hour later Koroshiya woke up with bandages around her torso.
"So you finally woke up," the woman from before said, "bandaged you up."
"Thanks . . . Who are you?" Koroshiya said starting to sit up.
"My name is Irina Jelević," The woman said.
"I've heard of you, you're one of the most successful assassins right," Koroshiya said in awe.
"You know you're stuff, mind telling me why you were bleeding earlier," Irina said.
Koroshiya thought for a moment, "It's my training teacher he beats his students when they don't listen."
Irina looked at her in shock, "but then why don't they fire him."
"Because he's a master of deception, the only reason why I'm even here is because my father's stupid protege sold us out, I've been training to be an assassin since I was 4." Koroshiya explained.
"So why don't you just escape," Irina said.
"Trust me if I could I would've a long time ago," Koroshiya then points at her arm, "They have a tracker in my arm. I could take it out but I couldn't do it while that guy was here plus I usually wouldn't have enough energy."
"How are you even supposed to take it out," Irina asked.
"You have to cut it out or find a way to deactivate it but that is not possible because it's monitored 24/7" Koroshiya said taking out her survival knife.
"Wait you're doing it right now?" Irina said.
"Well why wait I am not dealing with another beating from my teacher," Koroshiya said cutting into her skin.
"You sure that's a good idea," Irina said.
"You got a better one," Koroshiya said wincing from the cut.
"Here use this," Irina said while handing Koroshiya a pair of tweezers.
"Thanks Irina," Koroshiya said grabbing the tweezers then takeing out the tracker.
Irina then handed over some bandages with disinfectant.
Koroshiya cleaned and bandaged the cut.
"Never got your name," Irina said.
"It's Koroshiya, and now I can finally leave this hell hole," Koroshiya said.
"You can come with me if you want you could meet my mentor and learn to be an assassin again," Irina offered.
"Sure I have no where else to go since my father was taken," Koroshiya said.
"Who was he," Irina said as they walked out of the house.
"He wasn't my real father but he was the closest thing I had he was a top assassin but he never said his name," Koroshiya said.

For the next few months Koroshiya was being taught by Irina's teacher Lovoro. After those few months Koroshiya started to go with Irina on her assignments to help get intel so Irina gave half the money most the time. Koroshiya even went on a few of her own assignments.

"So you want me to attempt to kill this octopus like creature, who will blow up the earth in March if he doesn't get killed," Koroshiya said sitting on a couch with a paper that had a creature with a round yellow face. She was sitting in front of agents from the Ministry of Defense.
"Yes the reward is 10,000,000,000 yen," One of the agents said.
"I'll do it, but on one condition," Koroshiya said.
"And that is," Another agent asked.
"The bounty on my and Irina Jelević's head gets removed," Koroshiya said.
"That can be arranged," the first agent replied.
"Then we have a deal," Koroshiya said.
"You will be joining class 3-E of Kunugigowa Junior High, you will be escorted by Tadaomi Karasuma one of our agents who is working as the P.E teacher," The agent said.

E N D  O F  P R O L O G U E