Hanabira Uchiha
Hanabira Uchiha (内葉花びら, Uchiha Hanabira) is one of the last surviving members of Konohagakure's Uchiha clan. After her older brother, Itachi, slaughtered their clan, Hanabira and Sasuke made it his mission in life to avenge them by killing Itachi. She and Sasuke is added to Team 7 upon becoming a ninja and, through competition with his rival and best friend, Naruto Uzumaki, Hanabira and Sasuke starts developing his skills. Dissatisfied with her progress, she defects from Konoha so that she can acquire the strength needed to exact her revenge. Her years of seeking vengeance and her actions that followed become increasingly demanding, irrational and isolates her from others, leading her to be branded as an international criminal. After learning the truth of her brother's sacrifice and later proving instrumental in ending the Fourth Shinobi World War and being happily redeemed by Naruto, Hanabira and Sasuke decides to return to Konoha and dedicates their life to help protect the village and its inhabitants becoming referred to as the "Supporting Kage" (支う影, Sasaukage).
Hanabira is the third, youngest child and only daughter of Mikoto and Fugaku Uchiha; they named her after the flower's petal in the hopes that she would someday be bloom to be strong and known of her beauty. Hanabira and Sasuke grew up in the shadow of her older brother, Itachi, a natural prodigy who many in the Uchiha clan and the village would constantly compare Sasuke and any of his accomplishments to Itachi. Hanabira herself adored Itachi, never passing up an opportunity to spend time with him. Although Itachi welcomed her company, letting Hanabira watch him train and taking her on adventures into the forests, Itachi in return rarely helped Hanabira and Sasuke themselves become a better shinobi; when asked, he would often instead poke Sasuke's forehead and promise to do so some other time. Hanabira and Sasuke found this annoying, but didn't allow it to blemish her high opinion of her brother.
On entering the Konoha Ninja Academy, Hanabira proved to be the standout of his class, consistently getting top grades. However, he could never meet the same milestones Itachi had set, resulting in their father paying Hanabira little attention. Aware of this neglect, Itachi, despite being increasingly busy, tried to stand in for their father by giving Hanabira and Sasuke the recognition he craved, at times even blackmailing Fugaku to spend time with Hanabira and Sasuke. As time went on, Itachi started becoming distant with and cold towards their family, culminating in a falling out with much of the Uchiha clan on their suspicion that he'd killed his best friend, Shisui Uchiha. Hanabira and Sasuke did not understand the reason for this, but he didn't mind the side-effect: his father began taking an interest in his development. Fugaku taught Hanabira and Sasuke how to perform the Great Fireball Technique, which she mastered in a week. Fugaku stated his pride in Hanabira and Sasuke for this accomplishment, but at the same time encouraged her not to follow in Itachi's footsteps.
After a long day of training, Hanabira and Sasuke returned home one night to find the streets littered with the bodies of the Uchiha. They rushed home to notify her family of this Uchiha Clan Massacre, only to find Itachi standing over the bodies of their parents. Hanabira and Sasuke tried to solicit help and comfort from Itachi, who responded by using Tsukuyomi on them to torment him with visions of him murdering their family. Horrified by what Itachi had done, Hanabira and Sasuke pleaded for an explanation, to which Itachi replied that it was to test his own power. Fearful that he would be next, Hanabira and Sasuke tried to run. Itachi cornered them and explained that Hanabira and Sasuke, as she then was, would not be worth killing. Only by becoming stronger, such as by acquiring his own Mangekyō Sharingan, could they prove a worthwhile challenge to Itachi's abilities. Before leaving, Itachi encouraged Hanabira and Sasuke to hate him, to desire revenge, and to gain power from that. Hanabira and Sasuke immediately followed through, pursuing Itachi and using their newly-awakened Sharingan to attack him. The attack failed, Hanabira and Sasuke passed out, but not before glimpsing Itachi crying; Hanabira and Sasuke would forget this had happened for many years.
Hanabira and Sasuke, now one of the last surviving Uchiha, was alone. They spent the first few days after the massacre wandering her family's compound, reflecting on the people who were now gone, killed by Itachi. Hanabira decided to do what Itachi had instructed and dedicated her life to vengeance, having no other interest than bringing about Itachi's death. She threw herself into her studies at the Academy, making no efforts to form friendships and ignoring all of the boys' attempts to gain her affection. One of her classmates, Naruto, disliked Sasuke's cool personality and the attention she received and developed a one-sided rivalry in his pursuit to prove herself just as good as, if not better than, Sasuke. For her part, Sasuke thought little of Naruto and was usually annoyed by his outbursts, but would, at times, secretly smile at how hard Naruto worked because of her. Ironically, for all the attention she received, Naruto was the only person among her peers who understood Hanabira and Sasuke due to the painful experiences they had.