~Akito~
Let's start with Yuki's father Akito Fujita. Akito was born in a non-ninja village that hates strangers and mostly kept to themselves. His mother died after giving birth to him and his father saw him as a curse thanks to his kekkie genkai believing his wife cheated on him and left him her mistake. His Kekkie Genkai was to regenerate cells. He heals a lot faster then normal and could heal others if he tired. He mostly healed himself usually. The town people weren't friendly with him either he was a thief and a little too clever for his age. His father the drunk wasn't much liked either being the town drunk, he used to abuse Akito a lot and test how far the Kekkie Genkai can go. At age eleven after his father tired to kill him Akito killed him in self defense, not feeling any fear or anger or even relief he grabbed his stuff and left his home town.
There he met an rough ninja from Konoha that was in the bingo books. The man taking pity on Akito he taught Akito how to read, write and do math. Akito was a quick learner and eager to learn as much as he can, he also trained Akito to be a better fighter, the stayed for three years before he departed during their travels. Akito started to use his skills to be an assassin for hire. Many small villagers or ninja's used his skills to catch their enemy. He was known as the red Assassin mostly for his red hair.
After a few years of being called he opened up to a young girl named Yuki. She was a daughter of a village chief a man he was supposed to kill she was so kind to his 17 year old self. He was assigned to kill her father and he never left a mission unfinished but years of being cold and unloved was feeling the warmth of a child. He killed the father but she saw his kill and was scared of him. Broken hearted for the first time Akito decided to open up.
He spent another five years exploring the world with a fresh new look, he made friends from different places and was more careful with his missions he took. He made a lot of enemies but because of his skills no one really messed with him. He finally made it to Konoha after a long while because of his skill and Kekkei Genkai he caught the eyes of certain elder who wanted to use him. Lucky for Danzo he fell in love and was willing to work under him for his daughters hand in marriage .
~Natsumi~
Now Yuki's mother her story is simpler then Akito's story but has a tragic ending. Danzo on drunken night and jealous of his friend Hiruzen ends up at Brothel outside of Konoha one drunken night. He needed to let out some sexually reprised desires as he trained himself to reprise them and ignore any pretty woman that walked past him. As you can imagine he let his guard down that one drunken night and made love to one of younger girls there. She was pretty well curved and had a sharp tongue, they had one night together, he left the next morning regretting his mistake.
A year later, the woman appeared in front on his door with a baby, it was his. Not wanting his DNA out there their in the world he brought the woman back and she became his wife and they tired to raise their daughter together. After three years, she had a enough she missed the freedom of the outside world, Danzo kept everything dark and he was too strict. He never raised his hands at her but she was getting sexual frustrated.
She one day packed her stuff and left, she figured daughter was in safe hands. Konoha was a wonderful place and Danzo though cold her daughter would be fine as the people around Danzo weren't so cold.
Natsumi was always seeking her father's approval desperate for father's love and attention. He seemed more impressed with strong ninja's so that is what she trained to be but she is a bit clutzy as a ninja and always made mistake. She could handle herself on missions but she wasn't what her father would be impressed with.
She also used to cause a bit of trouble to get her father to notice her, becoming a gang leader of a few trouble making ninja's. They would cause minor fights with people vandalize a few things People would avoid them if they can but honestly there weren't a threat. And Natsumi couldn't get into too much trouble due to her father's influence and she feared him still.
She got really jealous when red haired man with a mysterious past caught her father's attention. She used to try to cause him trouble have him trip up or lose his mission papers or even fight him. But he was too skilled for her and would run away from their fights but he was always gentle with her. He never humiliated her and would save her from her own mistakes when she made them.
His kind dark eyes were the kindness she was looking for, she found herself falling in love with him. He would train her own a few skills to help her become a better ninja, they would go on dates soons he was causing less trouble for her father. Her father was excited when Akito asked for her hand and marriage and was quick to tie the knot for them, both of them were married both were happy and both had a family they craved for after they had their daughter Yuki.
~Yuki~
Yuki was married into a family full of love. Both her parents were desperate for their own family finally had the daughter they loved and planned to have another child when Yuki was old enough. Now Akito did work under Danzo but he wasn't stupid, he knew what Danzo was after and used himself as a genie pig to protect his family. Natsumi not so much, she did quit being a ninja to raise her daughter. Akito was always running missions and was out of time being Danzo's favorite just through his skills alone.
Still he would bring his daughter trinkets from his travel and train her when he had time, despite not wanting his daughter to be a ninja being. He would also spend a lot of his time teaching her things, he was lucky as she had skill for learning new things quickly and her mothers skill for being a ninja.
Buy the age of three the Kyuubi attacked the village, Akito was out of town on another mission. Natsumi eager to protect her daughter went to go the mountains for safety she was three years out of practice and her skills as a ninja were average. Yuki a bit scared wiggled out of her mothers arms went back to her room to find her box of father's trinkets not want to leave them behind, but a giant piece of rubble was heading her way her mother seeing this pushed her daughter out of the way and in the end died saving her daughter.
Yuki seeing her mother pass away before her eyes was broken, she passed out crying trying to get her mother to move and follow everyone. Akito came a little after the Kyuubi was captured to find his daughter passed out and his wife dead. Furious at himself he vowed to keep Yuki safe and forbid her from becoming a ninja ever. He sealed up her kenkai genkai so Danzo won't use it and she can't use it either. The Kenkai Genkai though powerful side effect if too much use turns blood vains black. Akito wore medical tape around his hands and arms, if the vains touched his heart he would die.
Akito took more time off after his wife's passing and during those times he would teach Yuki different things. Akito felt that books were the most powerful weapon in the world and knowledge was power. He wanted Yuki to be well trained, he taught her many things making sure she could handle herself in tough situations and nobody would look down on her.
Yuki actually loved it a lot, she loved her time with her 'papa' and worked hard to keep impressed with her skills she learned. Akito basically trained Yuki to be an assassin without learning how to kill or fight. He wanted his daughter well balanced and Yuki was quick learner. When he did go on mission he would leave her with homework she would have to complete before eh cameback. He also wanted his daughter to have brighter view of life and people around them.
Akito was Yuki's best friend. She loved her time with her father she loved showing off her knowledge in front of him and learning so much things that book couldn't begin to teach her. She didn't never held anger towards her father for stopping her from becoming a ninja and when her father was around he showered her with love.
Akito began becoming a spy for Danzo on the Uchiha clan he disagreed with it. He respected the Uchiha a lot and the hate Danzo was spilling on the village with the Uchiha went against his principles. He had felt anger towards the Uchiha at first but he figured it was punishment for the mistakes he had done in the past and he would go back to his past self if he late the hate consume him.
Itachi met Akito once on a mission, Itachi liked Akito for his skill and kind philosophy that matched Itachi's. He would be part of the darkness to protect the loved ones and the journey to peace had to shed some blood from those who were in the darkness. He also found Akito a bit obsessive of his daughter as he would change subjects to brag about her. He also remembered Yuki hiding behind her father's legs too shy to make eye contact with him.
At age eleven on Yuki's birthday her father had to go on a mission, Yuki was so angry at her father for leaving her on her birthday, she shouted she hated him for the first time and ran away to her room to hide. Her father only smiled kind smile and told her he would see her soon. It was the last time she saw her father, Akito tired to defy Danzo and warn Fugaku of the plan and lost his life.
The trauma of losing both parents wounded Yuki. Akito taught her many things but he never spoke of death to her. Both of them never healed from losing Natsumi and neither spoke of the pain the felt. Yuki feeling it was her fault her mother died and Akito feeling it was his. Yuki had hidden her mother's death in the far reaches of her heart never to be opened the same goes with her father. Despite seeing his body being hauled away it broke her little heart to the point she lies to herself and everyone her father is alive and on a mission. She never opened the letter her father left her for her birthday.
Yuki went under Danzo's care, thanks to the seal Danzo couldn't extract cells from Yuki's body for the kekkie genkai. Like Aktio Danzo began teaching Yuki different ways of thinking, instead of being smart and wise he made her clever too. He taught her the way of politics, how to read for people's weakness and manipulate them. He figured teaching her these skills he could use her as a pawn marry her off and she would produce a heir. She would be his face on social gatherings keep her eyes and ears on the streets and because she was pretty for her age she could attract suiters.
But Yuki was too clever, she unlike her mother would fight back against him despite her fear for him. She felt fear for him and would avoid him and like her grandmother before sit where their was always light and she was better with people then he was creating deals that he could use to take advantage of but she was a dreamer she wished to travel eh world like her father did.
Yuki went to the medical field, she was smart and could handle the field well but her lack of charka control made it difficult for her to explore the world. She was good at politics but she only really wanted to help people. Politics had too many questions not enough answers and nothing was correct. Being a doctor usually ahd one answer. Still she struggled.
At age 14 she was captured by a couple of thugs who wanted to use her as a hostage and get money from Danzo. They had planned to kill her right after, but they ran into Itachi Uchiha. Itachi saved her ass and brought her back to Konoha after they went through a small mission in a small village. He asked her what she wished to do and she said she wished to travel gathering her stuff he helped her leave Konoha.
Yuki and Itachi travel off and one together solving small mystery from village. Yuki helping people with her herboligy skill and what her parents and Danzo taught her. She is joined by Akihiko, a spy for Danzo who is supposed to keep his granddaughter safe and out of trouble. When Itachi is gone both of them are going through their own adventure. Yuki's travel does help her get the closure she needs, her father would leave little letters after every mission with a friend of his in hope that his daughter would travel the world like he did.
Yuki and Itachi fall in love slowly, Yuki's harsh words but kind attitude try to get him to push forward in life. And Itachi's hidden kindness and softness towards her both do fall in love and secretly dating.