Mito Uzumaki

was the wife of Hashirama Senju, the grandmother of Tsunade and Nawaki, and the first jinchūriki of the Nine-Tailed Demon Fox.

Background
The Uzumaki clan and the Senju clan, being distant relatives, had always had close ties. For this reason, Mito married Hashirama Senju, who would help found Konohagakure and become the village's First Hokage. After Hashirama's victory against Madara Uchiha at the great battle at the Valley of the End, and arresting control of the Nine-Tails from him, Mito used her clan's unique fūinjutsu, and sealed the beast within herself in order to keep the threat Nine-Tails posed contained. Despite the seal's strength, it almost broke at some later point when Mito was going through childbirth. Eventually, her husband died in war, and Mito was left a widow.

Towards the final years of Mito's life, it was decided that a new host for the Nine-Tails would need to be found. Kushina Uzumaki, one of Mito's kinsmen, was then selected for the role due to her special chakra, and was terrified by the idea. Mito comforted her and, before the transfer was performed, told Kushina that love was the only way to tame the Nine-Tails' hatred, and have a happy life.

Appearance
Mito was shown to have worn an elaborate kimono and a kind of tiara in her hair. Her hair was seen arranged in buns similar to Tenten and she had a diamond mark on her forehead, similar to that of her granddaughter Tsunade. She also has what appears to be seal tags in her hair decals.

Abilities
Not much is known about her fighting skills but Kushina said she was a powerful kunoichi. She was proficient enough with fūinjutsu to seal the Nine-Tails within herself and is remarked as having incredibly potent chakra capable of restraining the beast. Due to being a member of the Uzumaki clan, Mito had an exceptionally long life.

Quotes

 * (To Kushina)