The Last Master
Kushinada Chikage enjoyed life while she could...because one by one, she lost her friends to either getting killed to preserve peace, or time itself.
Because of the failed Sunset and her own actions during war, she was abandoned by her Master that her education in Kushinada-Ryuu was incomplete that she can never master it. But at least she knew the longevity techniques and the diet needed. But she was upset for the abandonment for fighting for their honor that it didn't go well with other Masters...at least she had people to turn to and knew true comradeship. Like Kanou and Shirahama, she became a Mixed Martial Artist as a result and in return, she shared the longevity technique and diet of Kushinada.
She still outlived everyone because its not easy, to create a peaceful world where in the shadows, people start trouble and kill. And the others are such hotheads thus one by one, they left her alone by dying.
Using her vast inherited wealth, she built a dojo in the mountains, adopting young orphan girls into her family to preserve the martial arts of her friends, knowing who suits what art and training required, but all of them followed Kushinada-Style Longevity. She trains only girls as girls are better at keeping calm than boys, if raised since young into it. Children follow by example after all. She doesn't let them go to school until Junior High, home schooled for years.
While within her large room full of knick-knacks of precious mementos. She clings hard as to not feel lonely as one by one, her students grow up into fine ladies fighting for what's right, before settling down and have families of their own, and teach their children their art.
Then when she was 70, as a woman appearing 20 as her master had, humans with superpowers started to be born...even her students' descendants came to her for help as either they had no idea what to do, or their husbands and relatives rejected the children, seeing them as freaks.
So Chikage took in these superpowered kids and mutant kids and had her students rescue them from persecution but she can only have so much room, so her students have to do the rest themselves.
Sometimes, she was glad her location's a secret, as the world fell into chaos.
As chaos and unrest ensued due to the outbreak of powers, ordinary civilians with their own powers decided to take matters into their own hands to bring order to society and thus the first Heroes appeared in the form of Vigilantes and thus beginning the Vigilantes Era. Much of whom, are her own students and their children. What was happening now, reminded her of the X-Men comics back when she was fourteen when Sakaki once introduced her to comic books to help her have a chance of a childhood before it's lost forever.
During this time period, a man called All For One became a symbol of unity in society. He used his Quirk to remove Quirks from those who did not want them and give Quirks to those that did. His actions under the guise of returning society to its prior state of humanity, when in reality, he was gathering followers who were loyal to him, allowing him to act out his ulterior motives. He caused such chaos that her students protected anyone with powers he absolutely cannot have under her leadership that she came out of the shadows as the Final Grandmaster of Martial Arts, going to war once more.
She also met his younger brother once who hoped to stop his older brother, but what can he do with a Transfer power and the Stockpile granted to him that merged together somehow?
'I will train you to gain power for that Quirk.' she decided. 'It will not be easy. Once you reach age of retirement, you will pass on that power to a younger successor. I will train them as well until that power stockpiles enough from all wielders to become a power powerful enough to defeat All For One.'
So the younger brother endured a lot of hell from Chikage, until he chose a successor among her children to pass the power he called One for All.
'One for All?'
'Yes, sensei...I want it to oppose the selfishness of my brother, and become a power that is used for the sake of others.' said the younger brother. 'This is my will. My hope. The only power he can never steal!'
'...good thing I'm quirkless.' Chikage shuddered. But she has immense Sei Ki in turn that she cannot take in One for All, otherwise, the next holder will blow up!
Thus One for All chose a boy in Chikage's care, before ultimately retiring in her residence for good, now a powerless man who worked hard to nurture his Quirk and they raised his successor together.
However after that, she lost track of One For All due to doing so much, after the first died. All she knows is that the power is still alive.
As society adapted to the new status quo while war against All-For-One went on in the shadows, the Police Force moved to prioritize leadership and to maintain the status quo, and as such, decided not to use powers as weapons. To fill that void, the profession of crime-fighting power users, Pro Heroes, began to exist which caused the Vigilantes to slowly disappear. Authorizing the use of powers that could so easily kill, however, was a greatly criticized decision at first.
Over time, it came to garner public support due to the fact that the first people to work professionally as heroes acted morally and upheld the law, so Hero Schools are built, after curriculum and upbringing was decided upon, and choosing who are allowed to become Heroes or expelled for not having the right mindset. U.A, Shiketsu, and Ketsubutsu are built. Only three Hero Schools allowed in Japan. However, some members of society were not happy with the governments' regulations on power usage as they believed that the free use of their superhuman abilities should be a basic human right. This was started by a woman who cried for fair treatments for her child, saying, 'It's only his Quirk!'
A group of Quirk users known as the Meta Liberation Army, led by Destro, had tried to stop the passing of regulations that would restrict power usage, calling it Meta Ability. They rebelled against the governments of a number of nations for several years before ultimately suffering defeat.
Took a while for things to calm down, that now, society was black and white. Your destiny is decided whether you have a quirk or not, heroic or not, a new brand of prejudice happened...that Chikage took to saving Quirkless Children next, as well as abused children just for having either useless or villainous Quirks. She would adopt them all and give them a life that she toured Japan for Quirkless Children.
She would take them in every ten years as the room in her vast estate, is limited. There was also the issue that her wealth is running out, and she can finally feel her age that she didn't have long left to live now. 20? 30? 40? at most? Or less as she is oh-so-old? And she now rightfully appears 50 physically.
She was way older than that brat All-For-One.
She lived this long to create new generations of champions but her time is almost up.
"I feel I did enough...before I go home to everyone again soon." Chikage smiled. "I did the world a lot of good in my own way. But now, I am so tired...but I need one last hurrah before I go. One last champion, and that's IT."
She went to prepare her Last Will to her true successor. Still nameless...for now.
Out of sheer dumb luck, she eventually tracked down a young man who was dying, passed on the power to a young girl named Kamado Nana. Her Quirk was Float. She began training Nana in the ways of Martial Arts, honing her body and her Ki. Somehow, One-For-All felt a calm presence, not one shred of Dou presence since it left Ayanokouji Reiji, the second holder. Did the other holders somehow possess Sei Ki even if untrained? Oh, well.
She became Nana's Hero Trainer and mentor growing up, meeting with the girl every after school, honing her body, her ability to use Ki, trained hard in Hakkyokuken due to her body's ability and her ki training was started as a child too, at 9 years old when she met the dying sixth holder, whose name they don't know. He spoke enough to tell Nana about One for All, All-For-One and the battle that spanned decades, before passing his will and power before dying. Poor kid died young in his twenties.
At age 15, Nana entered U.A High School, bulldozed her way through the exams and scored herself a spot, capable of using the powerful Quirk without...blowing herself up.
But her training never stopped as the more training she did, the more access she has to One For All until she married her husband Shimura Kazuya at age thirty. So Chikage returned to her Hermitage, thinking she would be fine...until she sees in her TV that Nana was killed, and she later had a phone call.
'Yes?'
/Uhm, i-is this Kushinada Chikage?/ it was a distraught teenage boy. /Nana-sensei said to contact you if anything happens to her...I'm currently the new holder of that Quirk, Yagi Toshinori...she passed the Quirk to me before her fight./
'I see. Where should I meet you?' Chikage asked him.
/At sensei's old apartment...it's at.../
xxx
Nana's old apartment...
Chikage arrived in three days to the location to meet a distraught blonde boy at high school age. He was with a man in his forties with white hair and an all-white suit, and yellow boots and cape.
'So, you're Nana's successor.' Chikage spoke to him. 'At what age did you get One For All from her?'
'You're Kushinada? Dang, what'd you do to stay young?' the older Hero wondered, bamboozled as he learned about her from Nana, yet while she was older than him, he looked older than her in looks! 'Nana talked about you and she was a dang fine Hero who rose to Top One status...well, didn't stop her from dying, innit?'
'This foolish Quirk-Oriented society caused imagination, innovation and creativity to die young.' said Chikage somberly. 'My teachings...sure she rose to Top Hero status yet she still died...this quirkist society killed her. Their stupidity that they passed on to the youngsters.' she shook her head. 'Otherwise she never would have died. Frankly, young Yagi is also sadly, indoctrinated to this foolishness, so I haven't much hope for him to last long either.'
'T-that's!' Toshinori cried in protest and indignantly.
'I will train you as per her last wish.' Chikage told him. 'However, plan ahead for your successor. Either that, or I find someone younger, young enough before their minds are poisoned by Quirk Doctrinations.' she told them coolly. 'Quirk Prejudice as its either you have a so-called hero, villain or useless Quirk or people decided your future for you based on your Quirk when you have a brighter future than that, Destiny Indoctrinations, Quirkism, those things are poison to the mind. Why in my day when I was your age, people are creative. Innovative. They never stop discovering things and exploring their world. This era is so stagnant and simple-minded. Disgusting.' she told them disdainfully.
'...not to be rude, but how old are you exactly?' the other man asked her. 'Nana told me about you and your training together...she was mid-thirties yet she didn't look the part she once complained to me that people are thinking her husband married a high schooler!' he chuckled.
'You can say that I'm 90 years older than that brat All-For-One.' said Chikage much to their shock. 'I was a martial artist who learned Kushinada-Style Jujutsu, and their longevity techniques and diet. By the time that damn brat was twenty, I appeared physically 20 despite being nearly a century old.' she informed them. 'But alas, I can feel my time coming. Half a century at most to go before I finally die, and rejoin my friends and comrades. My fellow Martial Artists.'
'Training with me involves a strict regime and diet. Until you master One-For-All, no such things as Western Food and Yoshoku for you as well as junk food, alcohol and sweets. If Nana can do it, so can you.'
'...we need to gather the right people for this.' said Gran Torino grimly. 'Toshinori will have to enter U.A High School for his safety.'
'Mm.'