Aerith

Aerith Gainsborough is a character who lives in Traverse Town in Kingdom Hearts and Kingdom Hearts: Chain of Memories and Hollow Bastion/Radiant Garden in Kingdom Hearts II. Like most of Sora's allies, she originates from the Final Fantasy universe. Aerith is voiced by Mandy Moore in Kingdom Hearts, Mena Suvari in Kingdom Hearts II, and Maaya Sakamoto in the Japanese versions of both games. She has a particularly minor role compared to the other Final Fantasy characters. This is most likely a due to the off-hands role she played after her fate in the original game.

Kingdom Hearts
''She lost her home to the Heartless at a very young age. Beneath her gentle disposition lies a strong will and a firm sense of duty. Many are naturally drawn to her. Aerith works with Leon and Yuffie to learn more about the Heartless and the "key". "Final Fantasy VII"''

Kingdom Hearts: Chain of Memories
''A young woman who fought the Heartless. Her calm demeanor hides an unbreakable will.''

Aerith also has a mysterious sense of truth, and is aware that Traverse Town and it's inhabitants are a figment of Sora's memory.

Kingdom Hearts II
''A young woman whose quiet eyes belie an unbreakable will. Like Leon, she met Sora while living away from her hometown, and helped him now and then on his journey.''

Now Aerith works with Leon and Yuffie to restore the town to its past splendor.

Kingdom Hearts
Aerith is encountered by Donald and Goofy on the first trip to Traverse Town, where she explains the nature of Ansem's Report, as well as the Keyblade to them. She had a few more appearences along with Leon and Yuffie. Later, she showed up in Hollow Bastion after Xehanort's Heartless dissapeared, and spends her time studying the Heartless's research in Hollow Bastion's library. Talking to her will allow Sora to learn "Curaga", the strongest cure spell in the game. During the end credits you can see her inside the library, being reunited with Cloud.

Kingdom Hearts: Chain of Memories
An image of Aerith appears, along with Leon, Cid, and Yuffie, in the memory-based Traverse Town in Castle Oblivion. At first, she, like the other characters, expresses disbelief that she seems to know Sora despite not remembering him. After speaking with Sora, however, she comes to realize that she is just a projection based off his memory of her. She and Maleficent in Riku's game are the only ones to realize this.

Kingdom Hearts II
Aerith is a member of the Hollow Bastion Restoration Committee. In Kingdom Hearts II she wears a modified version of her Before Crisis outfit, only with a red skirt instead of a green one. She helps during the invasion of Hollow Bastion by healing Yuffie and presumably continues to aid other characters or fight against the Heartless. Aerith assisted Sora later in the game during his movement against the MCP by downloading the deletion program. In her last appearance of the game, during the ending credits, she is seen sitting on a ledge and looking up towards the Radiant Garden sky, possibly wondering what happened to Cloud and Sephiroth after their fight at the Dark Depths (assuming the player has completed the sidequest to obtain Fenrir). Throughout the story she encourages Cloud to do what he must to fulfill his goals, and she is sure that destiny will lead him back to her. She is one of few characters whose name is never spoken during cutscenes, only written in dialog boxes or menus.

Abilities
She is able to cast cure magic, as evidenced by her brief appearance during the invasion of Hollow Bastion in Kingdom Hearts II.

Though she is never seen in battle, she may have some battling capabilities when she asks Leon to let her protect Ansem's Study while he goes to help Cid and Sora and the others head into Space Paranoids looking for Tron.

Trivia

 * There has been some confusion over Aerith's name over the years. In the original Japanese version of Final Fantasy VII, her name is Earisu, which is pronounced "Aerith." But when the game was released in the United States, her name was changed to Aeris. When Square Enix released Kingdom Hearts, they decided to put the confusion to an end and officially changed Aeris's name to Aerith, as it was originally meant to be.
 * It is shown in a cutscene in Kingdom Hearts II and at the ending of Kingdom Hearts after the credits that Aerith has a close relationship to Cloud Strife. This is most likely due to their relationship in Final Fantasy VII, at the end of Kingdom Hearts after the credits Cloud is seen in Hollow Bastion meeting up with Aerith. In Kingdom Hearts II they have a conversation in front of Sora and his party where she mentions that Cloud will be lead back to her sooner or later.