Yuffie

Yuffie Kisaragi is a character from Final Fantasy VII who makes an appearance in all Kingdom Hearts games. She travels with Leon, whom she mostly referred to by his real name sometimes to his annoyance. She ocassionly refers to herself as the "Great Ninja Yuffie", wielding a large wind-blade shuriken as her weapon.

She is hyperactive but tires out easily because of it. She always tries to do her best and is very optimistic.

Kingdom Hearts
''A female ninja who escaped to Traverse Town when her home world was taken by the Heartless. She stays strong and cheerful in any situation. She works with Leon and Aerith to unravel the secret of the "key".''

Kingdom Hearts: Chain of Memories
''A girl whose cheerful personality belies her painful memories. When she was still young, the Heartless robbed her of her home.''

Never one to sweat the small stuff, Yuffie seems unfazed by her fuddled memory.

Kingdom Hearts II
One member of the town's Restoration Committee, a spirited girl who actively does her part to keep tabs on the town.

''Yuffie met Sora when she was living away from her hometown. Thanks to his help last time, the Heartless were ousted and she got to come home - so she's very grateful to him.''

Kingdom Hearts
Sora's first meeting with Yuffie is in Traverse Town, where Sora accidentally mistakes her for Kairi. Yuffie doesn't have that much of a role in the game, but she, along with Leon, was the one who told Sora about the keyblade while in the hotel of Traverse Town.

In the fight cups at Olympus Coliseum, Yuffie is one of the bosses to defeat in order to win a cup. In that respect, she uses magic and her shuriken against Sora, Donald and Goofy.

Kingdom Hearts: Chain of Memories
Modeled after the real Yuffie based on Sora's memories. She doesn't remember Sora, but Sora's heart makes her remember, which she classes as strange yet convenient.

Kingdom Hearts II
Yuffie features more in this game than the previous one. She is the first person to meet Sora as they enter Hollow Bastion and leads them to Merlin's house. There, she introduces the familiar friends from Traverse Town and the Hollow Bastion Restoration Committee (the latter of which she is a member of.)

She explains about the town's defense system to Sora, Donald and Goofy and, later on in the game, is one of those who helps fight alongside Sora in the Ravine Trail. When the heartless battle commences, she fights alongside the others.

Again, she is also one of the bosses to fight in the Hades Cup in the Underworld at Olympus Coliseum.

Battle
In battle, Yuffie uses slashing and throwing attacks similar to those of her Final Fantasy Counterpart. She also uses "Greased Lightning" to jump into the air and throw a shuriken. She can even heal herself by using her ability "Clear Tranquil". When enraged she will use "Doom of The Living" where she throws a gigantic, magically infused shuriken at her opponent. In Kingdom Hearts 2, Yuffie can teleport leaving smoke and blowing leaves behind. She uses her shuriken exculsively as a close range weapon this time around and has a powerful attack where she charges it up with magic and lets it fly around her.

Trivia

 * Yuffie was used instead of Rikku, as she was involved in Final Fantasy X-2 at the time. But traces of Rikku's intended attire remain on Yuffie during Kingdom Hearts and Chain of Memories. By Kingdom Hearts II, Yuffie wore the clothing she had on Final Fantasy VII: Advent Children.
 * In the Japanese version, Yuffie was voiced by popular seiyuu Yumi Kakazu, who also voiced Yuffie in other incarnations Final Fantasy VII.
 * In the English version of Kingdom Hearts, Yuffie was voiced by Christy Carlson Romano, who voiced Yuffie in Advent Children.
 * In the English version of Kingdom Hearts II, however, Yuffie was voiced by Mae Whitman who also voiced her in Dirge of Cerberus.