Kairi arrived at the Destiny Islands some years ago on a night, which saw shooting stars showering across the sky. She lost her memory that night and to this day cannot recall any details of her origins. Now 14 years of age, she has grown into a cheerful, strong-minded teenager who feels very much at home on the islands. Nevertheless, Kairi and her two best friends, Sora and Riku, decide to leave the Destiny Islands to learn more about Kairi's past. However, before they can set off on their journey, Destiny Islands are attacked by heartless. Kairi vanishes into sparkles through Sora´s arms.
Later, Kairi is found by Riku, but she was in a coma, her heart missing. Maleficent needed Kairi's heart to open the keyhole in Hollow Bastion and gave Riku power to fight for her. Sora travels to find Kairi and Riku , but Riku doesn't let Sora see Kairi. Being in love with Kairi, Riku wants to be the one to save her, and he was willing to do anything, even give into darkness, to do so. This causes a rift between the two friends who are both in love with Kairi. However, Riku becomes possessed by Ansem, and Sora must fight him to save Kairi.
Sora realizes Kairi's heart is inside him, so he stabs himself with a dark-keyblade and frees her heart. As a result of this, Sora's heart is also released, and he becomes a heartless. Kairi sees him in this form, but she can sense it's really Sora, and she saves him.
At the end of Kingdom Hearts, the destroyed worlds reform, and Kairi appears back on Destiny Islands. Just before, Sora makes a promise to her that they'll find each other again. Kairi is left waiting for Sora and Riku to return.
A year older, Kairi has grown into a strong, competent, young girl. The last time she saw Sora, he promised that they would always be together. However, Kairi cannot quite remember Sora. He has been erased from the minds of his friends during the events of Kingdom Hearts: Chain of Memories.
Kairi remembers everything when Roxas connects with her and tells her she is the girl Sora likes. Kairi is still living near Destiny Islands and wonders when the day will arrive that Sora will fulfill his promise. Also, a mystery surrounds Kairi, thanks to her connection with the witch artist, Naminé. Kairi grows tired of being left out and searches for Sora.
Kairi eventually fuses back together with her nobody, Naminé, and waits again for Sora and Riku to return. The three friends are finally happily together at the end of the game.
In this story, Kairi is still a little kid. She is living with her grandma at Radiant Garden.
She was pursued by the Unversed, this could be because she is one of the 7 princesses of heart and Unversed sense the light inside her. But she was saved by Aqua and Mickey, thus meeting Aqua.
In reason for saving her life, Kairi gives her flowers to Aqua and in exchange, Aqua gives Kairi some kind of protection.
Kingdom Hearts 3D Drop Distance
In the secret ending, Kairi comes with Riku to the mysterious Tower to see Yen Sid though Riku and Mickey have no clue why. Yen Sid then says he has heard she can wield a keyblade and says he wants to train her in the use of said keyblade for use in preventing another keyblade war.