TsunaSaku Reincarnation AU
AU where Uzumaki Mito and Nobi Sakura were each other's soulmates and long-time lovers until one day, Mito gets sent off to marry Hashirama and become the Senju matriarch. Sakura, desperate to see Mito even if she can no longer have her for herself, tags along and offers her clan's expertise. She becomes one of the founders of Konohagakure as well and becomes its chief healer just so she could have Mito near her. Mito has a heavy hand and huge influence on Konoha and the core of its political structure. Sakura sees Konoha as her and Mito's child and legacy of some sort, and decides to devote herself to it, exerting all that she has for Mito to Konoha instead. The Nobi of Uzushio are the pioneers of medical ninjutsu, and medical fuinjutsu together with the Uzumaki, their sister clan. In Konoha, Sakura takes the reins and lays the foundation of its medical department, and served as its Head of Health and Medicine until her death.
On the day Nobi Sakura dies and Senju Tsunade, granddaughter of Senju Hashirama and Uzumaki Mito, is born. Three years later, Uzumaki Mito dies and Uzumaki Sakura, granddaughter of Mito's cousin that took her place as the heir and eventual Uzumaki clan head, is born.
After Nobi Sakura's death, her estate, including all her works and researches, were bequeathed to the Senju. Tsunade had long idolised her grandmother's best friend, and one day, upon loitering around Nobi Sakura's old estate, she stumbles upon her lifetime's worth of medical ninjutsu, medical fuinjutsu, biomedical, and genealogy work as well as other techniques and researches. That was when her interest in medical ninjutsu began.
Uzumaki Sakura, as the heir to the Uzumaki and future leader of Uzushio, became a fuinjutsu master at a very young; as is expected of her. The fall of Uzushio happens, and Sakura is one the few Uzumaki survivors. With the chaos, shock and confusion, they got all separated and scattered all over the Land of Fire and its neighbouring countries. Somehow, she makes her way to Konohagakure, and by the virtue of Konohagakure's deep ties to Uzushio, as well as her being the Uzumaki heiress, she promptly gets taken in and becomes a ward of the Senju clan.
It is then that Uzumaki Mito and Nobi Sakura's souls find each other again.