Born in the Land of Iron to one of the countries top Samurai, Yumiko started high laugh in relative luxury. Due to her fathers position, their family was allowed many comforts that weren't common to normal citizens of the land. Her father would go off to fill his duties, while Yumiko was left at home to become the noble woman she was destined to be like her mother. At least that was the plan.
Her father always seemed to express a mild disappointment at the fact his first child hadn't been a son, one that he could raise to become a great Samurai like himself. What made matters worse was the lack of children after the birth of Yumiko, a doctor predicting that her mother was luckily to have even produced Yumiko. Her father toyed with the idea of producing a child via a mistress, though he knew such a child would be illegitimate and unable to receive the same level of honor as he wished for it.
His wish was partly granted though, as Yumiko turned out to be the complete opposite of a lady, rather she was much more interested in becoming a Samurai like her father. While she was young, the man humored the girl, and would often play fight with her, even teaching her basic skills. There was no harm in teaching the girl to protect herself he thought, especially due to his status which may put his family at risk. However he knew that she could never be a Samurai due to her gender.
As she grew however, the girl continued to practice the skills her father had taught her, and sort to learn even more. Despite her natural talent, her father refused, saying a female Samurai was completely unheard of, and that sending out woman to fight was a lowly task that only the Shinobi would fall too. This only fed the flame inside Yumiko more, she'd show all of them how great she could become, and how gender didn't make any difference in a person's ability at all.
Her first act of rebellion was to cut off all her hair, and disguise herself as a male. For a while she went undetected in the Samurai Academy, quickly drawing attention as a natural talent there as well. She picked up a number of skills at a rapid pace, outshining many of the older students as she worked her way up the ranks. However with this increased attention, she was soon found out and was the cause of much disgrace to her family.
After this the family kept a much closer eye on Yumiko, which made it difficult for her. Once things blew over a little, she managed to make her way back to the academy, and watch in secret. She would even practice long after the students had left on her own. However one night as she was training, a boy appeared, he wanting to gain his own extra practice himself. Having remembered the girl, and feeling bad for what happened, he offered to help her by teaching her what he had learned during the day, and in return she was be his sparring partner.
Together these two trained together in secret for years, both helping the other to improve in ways they couldn't alone. Yumiko was able to learn the techniques of the Samurai, and use her natural ability to master them, while her friend was able to gain the experience he needed to make up for his initial lack of skill.
Eventually as a teen, Yumiko came out of hiding, and stated she could beat any of the males her age in a duel. At first the boys just laughed and brushed her off, but after her continued taunts one boy decided shut the girl up. The boy thought he was all that, but before he could draw his blade Yumiko struck him down. Startled the boy crept away before he was seriously hurt, while the others started to take her more seriously. One by one, Yumiko defeated each of the males that dared to accept her challenge, despite the toll it was taking on her.
This event however due a great deal of attention, the Academy trainers trying to stop it, though they seemed powerless against the crowd of youth. As the final challenger fell, Yumiko's father appeared in a rage. He demanded the girl to stop immediately, but she refused, proudly declaring that she could even defeat him now. The enraged girl attacked the man before he could talk her out of it, and had to defend himself, resulting in a great battle, the likes of which those viewing had never seen. Eventually the girl just couldn't overcome the master Samurai, and fell before him.
After this event her fathers mind was troubled. He saw just how powerful his daughter had become, and it made him question if perhaps she should be allowed to train in his art after all. He knew such actions would never be accepted in their society, but nevertheless he decided to train his daughter in secret. Despite the fact she hated having to stick to the shadows again, she was grateful for her fathers acceptance and help.
As she became of age, it was clear what route the girl would take. With her parents blessing Yumiko left the land of her birth, and began a journey through the world, seeking to improve her skills in lands where woman were accepted as warriors. She planned to become renown for her abilities, and planned to return one day to show she'd become stronger than all the men at her home. She hoped then she could be the cause of change, and help others like her to be accepted.