Fuu was a kunoichi from the Hidden Waterfall Village who got stuck with the Seven-Tailed Beast, Choumei. She didn't last long after Akatsuki hunted her down—when they ripped Choumei out of her, she died along with it. That's pretty much her story in the main series, though she shows up later as an edo tensei zombie during the Fourth Great Ninja War, which gave her a second (weird) shot at relevance.
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