Yugito Nii

Yugito Nii was a ninja of Kumogakure. Yugito was also the Jinchūriki of the Two-Tailed Demon Cat. She was captured by Hidan and Kakuzu of Akatsuki, and later died as the result of having the demon cat extracted from her body.

Hidan and Kakuzu Arc
She is first seen running through the sewers from some unknown persons, later revealed to be Hidan and Kakuzu. When she enters a large room, where all the sewers seems to meet, she finally stops. After some bickering between the two Akatsuki members, she reveals that she intentionally led them there and activates an explosive tag on the tunnel behind them, sealing them off. Knowing that they are from Akatsuki, she swears upon her name that she cannot let them go, and she transforms into a miniature version of the Two-Tailed Demon Cat. However, after a 30 minute unseen battle, she is taken down by Hidan and brought to the Akatsuki lair by Zetsu for extraction, thus killing her in result.

Abilities
The only part of her abilities ever seen in the series was the ability to turn into a miniature version of the demon cat, giving her an upgrade in her abilities. The way she transforms is very similar to Naruto, being slowly covered in a dense fire chakra that takes the form of the Tailed Beast. It would seem that although letting go of the control to her Tailed Beast, she still have some control over the transformation and how much of its chakra that she can use. Nii in her in transformed state appears to use fire element and has extraordinary strength.

Trivia

 * "Ni" means "two" in Japanese.
 * Yugito and Kirābī are both Jinchūriki of Kumogakure.