stunKairi (カイリ?) is a best friend of Sora and Riku, and one of the seven "Princesses of Heart". She is an original character created by Tetsuya Nomura for the Kingdom Hearts series.[1] Nomura has stated that Kairi's name can be interpreted as "sea";[18] the Japanese on'yomi pronunciation of sea is kai (海?).[17] She is voiced by Risa Uchida in the Japanese version of the series and is voiced in English by Hayden Panettiere in the first two games as well as the prequel and Alyson Stoner in Kingdom Hearts Re:Chain of Memories and Kingdom Hearts 358/2 Days. As a child in Kingdom Hearts Birth by Sleep, she is voiced by Sumire Morohoshi in Japanese and Ariel Winter in English.

Kairi was originally a resident of Radiant Garden as one of the seven "Princesses of Heart". She has an encounter with Aqua in Birth by Sleep and is given a protective charm to keep her safe from darkness, which leads to her being sent to Destiny Islands when Xehanort performs an experiment where all six apprentices of Ansem the Wise forcefully rip out their hearts and caused the invasion of darkness;[20] in addition, she inadvertently gains the power to wield the Keyblade after touching Aqua's Keyblade. At the beginning of the main series, she is fourteen years old.[21] When Destiny Island is destroyed by Heartless, Kairi's heart is separated from her body and enters Sora's body. Kairi's body is in a deep sleep and can not wake up if she doesn't get her heart back. Her identity as a Princess of Heart is revealed along with the location of her heart. Learning of this, Sora gives up his heart in order to release hers and restore her heart back into her body. Soon after, Kairi finds Sora's Heartless and restores him back to human form. Kairi later gives Sora her lucky charm, which Sora promises to return. After Sora seals the door to Kingdom Hearts, Kairi is separated from him and left behind on the reforming Destiny Islands where she awaits his return.

During Chain of Memories, Naminé's memory-altering powers break the memories in Sora's heart as well as those of his friends on Destiny Islands, leading Kairi to lose her memories of him. In Kingdom Hearts II, Kairi and all of Sora's friends gradually remembers Sora as his own memories are restored. Kairi sends a letter she wrote out to sea in hopes that it will find its way to him. Later, Kairi is kidnapped by Axel, who hopes to use Kairi to lure Sora to him. However, Saïx takes Kairi from Axel and imprisons her and Pluto in a jail cell in the World That Never Was. She escapes her cell with the help of Naminé and they are saved from Saïx by Riku, in the guise of Xehanort's Heartless. Riku gives her the Keyblade Destiny's Embrace (デスティニープレイス?, lit. "Destiny Place") which she uses to fight off the Heartless that Saïx summons. Kairi reunites with Sora, and along with Donald, Goofy and King Mickey, the group face and defeat Xemnas. Kairi then returns with Sora and Riku to Destiny Islands where they receive a letter from King Mickey. As soon as Sora resolves to go on another journey, Kairi loans her lucky charm to him again. It is often hinted that Kairi has a crush on Sora, and that Sora has a crush on her too.