CAT IN THE BOX

THE BLACK CAT

You were born in Japan, your mother was a japanese salarywoman and your father well he simply never existed apparently, and while normally Quirks appear around the age of four you appear when you were born.with your mutation activated. The nurse who was taking care of you thought that you were dead since she couldn't find a pulse and you weren't breathing.your mother cried as she held your body thinking you were dead, the other doctors in the room found the same thing; and as they were taking you away from your mothers arms. She insisted on holding you at least once more even if you were dead. This ended up saving you as she thought of you being alive and wishing for it to be true she found you were breathing. After extensive testing and other people's viewpoints, though your quirk was some kind of immortality or regeneration quirk, in truth you were a "SCHRODINGERS CAT".
That information reached the at that time retired villain Kyudai Garaki who kidnapped you after killing your mother when you were just a baby, he tested and experimented extensively with you in a hidden facility, as he thought your quirk was unique and very powerful.

As you grew up, they tested your quirk in underground facilities and most people and scientists came to the conclusion that you were dead by all means, no vitals or signs of life, and any injury you sustained didn't matter as you still lived, even amputations were regenerated in large amounts of time this led you to believe and wish that you should be in fact dead, you only hope was the few moments of internet and videogames, and you wished someone would save you, and dreamed about being a hero like the ones the games you played (JRPG), you started to despise heroes and in twisted way embraced the pain seeing yourself as a tool or weapon. as you grew up in the lab you noticed things were weirder with you as you started to gain consciousness around 4 years old, first of all you didn't feel any pain and whatever damage you received was healed quickly (limbs grew in a matter of days) your cells while in a state of decay always returned and seek to keep its shape (this from your own perception of you being neither dead or alive and your quirk keeping the quantum uncertainty active), and this lead the scientist to start using you for more tests taking samples of your cells but hey quickly decayed, Kyudai Garaki noticed the principles of quantum uncertainty in you and decided to test your powers putting you to great stress at 4 years old forcing you to "die'' various times to trigger other possible hidden powers within you as he thought you were capable of manipulating quantum physics, this led you to understand and "awaken your power", you were able to teleport to your room when no one was watching you.
After that he presented yout to Shigaraki and weirdly in your broken state you were glad when he told you that heroes aren't good and that you will help build a better society, he was the same as you and you bonded with him seeing him as a brother even though at first shigaraki wasn't that fond of you, the love for video games and your fanaticall trust in him led to a good relation between you two, in which you wanted validation by him and Tomura on occasions was happy to let his childish side with you.
So at your fifth birthday you moved in with Tomura and grew among that forming league of villains and were trained you under different people believing you could be a great asset in the future to kill ALL MIGHT to who you had no love or respect seeing the he failed not only you but you're now big brother Tomura, among these you were trained by "Muscular" in hand to hand combat, and he was a great but ruthless teacher using his abilities without restrain enjoying killing you endless times; so you despised him but respected his strength, still you learned a lot from him. Besides Muscular, KUROGIRI teached subterfuge and tactics and you proceed great, even outsmarting Tomura on more than a few occasions.
So you grew up with him despising heroes and hoping to end them, training and playing, after time passed you reached your 14 birthday. You Tomura and kurogiri were sitting in the bar watching TV, eating cake that your "Aniki" brought "OI im bored lets play something, why do we have to watch the news it's the same boring stuff" Tomura looked at you and smiled annoyed "something interesting will appear, ALL might has been seen more and wee need to learn to win" he said sarcastically (in truth Kurogiri amd you both watch the news so to be informed of japan's news and culture) you simply yawned bored but Kurogiri spoke breaking the awkward silence "Well in fact there are news with knowing, U.A is about to start classes and the boss wants someone on the inside..." immediately you jumped like a nervous cat looking straight Kurogiri "HELL NO, i said it and i repeat it i don't want to join that place among all those wanna be heroes" Tomura smirked but didn't said a thing "Well Kobayashi seeing you are quite good at deception its logical, besides you are just the right age, and helping the boss in his plans is your dream right?", You looked at Tomura "Aniki say something, it will be boring as hell be with all those wanna be heroes, the only reason i would go in is to end the next generation right there" Tomura looked at you and simply said "If the boss says it you must obey, but i don't see the point in that".
Kurogiri looked annoyed, but suddenly he had an idea "Remember those games where the friend turns out to be the enemy? it would be a devastating blow to the heroes, besides Kobayashi you are very good at lying so i assume you will have fun" that made you think for a moment before agreeing, after all maybe you could have some fun...