Description
Kairi's appearance shows the most growth with aging of the trio of main characters. Typically Kairi has dark red hair, violet-blue eyes, a pale complexion, and a necklace with a silver bead that is only absent when she wears her school uniform. At age 14, during the events of Kingdom Hearts, she wears a white shirt with black surrounding the straps and collar that exposes her navel (most prominently seen in artwork), a purple skirt with a blue belt, and white slip-on shoes with purple caps. She also features a black choker, a yellow wristband as well as a purple arm band on her left arm and a pair of bracelets on her right arm. In Kingdom Hearts II Kairi is taller, her hair is longer and has become a darker shade of red, her bangs part to the opposite side, and her body has developed into that of a young woman. She dons two outfits in Kingdom Hearts II: her school uniform which features a white sleeveless shirt with a sky blue striped tie, a matching skirt with navy knee-high stockings and black shoes, and then her main outfit which mainly contains a pink strapless mini-dress made up of three zippers (two appear to be just decorative) as well as a white halter top underneath her mini-dress with a black hood. She also sports three bracelets on her left wrist, a black belt reminiscent of suspenders with a note book shaped bag attachment, and large lilac shoes. As a child, as seen during Kingdom Hearts Birth by Sleep and scenes from Kingdom Hearts, her hair is a little longer than it is when she's 14; she wears a white apron-like shirt with blue flowers and a blue line across the chest, a pink skirt with a white line on it and large, white shoes with pink and purple lines on them.
Older 15:

Younger 14:

Even Younger 4:

Personality
Kairi is caring, kindhearted and not afraid to speak her mind. However, she is determined and courageous when someone she cares about is in danger, often risking her own safety to help that person. She's also become slightly more withdrawn because of Sora's absence, having obtained wisdom usually beyond someone of her age. She's not as brash and bold as she was in the first game, but she's still pretty sociable. Kairi also makes friends easily, quickly befriending Hayner, Pence, and Olette in Twilight Town. She's usually always very cheerful and upbeat and seems to be bit of a tomboy as well. In contrast to Sora and Riku, who were both bothered by not knowing about Kairi's hometown, she took it in stride and was able to look at the positives about living in the Destiny Islands. She is loyal and headstrong, and she can be rather stubborn sometimes. While the bond between Sora, Riku, and Kairi is very strong, Kairi seems to be particularly important to Sora, and vice versa.

Equipment
Powers as a Princess of Heart
Because Kairi is a Princess of Heart, her heart possesses no darkness within it, leading to the unique birth of Naminé when she accidentally gives it to Sora, who later sacrificed himself to restore her heart. Should her heart be lost, her body will remain in a dormant state until it returns, as revealed in the first game when her heart was lost.
Like the other princesses, she has the power to open the Final Keyhole to Kingdom Hearts in Hollow Bastion once she is gathered with the rest of the princesses. This could be considered as the princesses' main power.
Kairi also appears to have some kind of latent magical ability, as seen when she manages to restore Sora's humanity after he becomes a Heartless. However, it could imply that she is only able to restore him because they share the strongest connection.
Since the other Princesses of Heart possess the abilities to hold back darkness and upgrade other people's powers, it is no doubt that Kairi can do so as well.
Aqua cast a charm on Kairi in Kingdom Hearts Birth by Sleep so that if she was ever captured by darkness, her light would lead her to the light of another. In an interview, Tetsuya Nomura stated it was this charm that lead Kairi to Destiny Islands.
She additionally has the ability to sense darkness, as the other Princesses of Heart are able to tell Sora of a great darkness nearby. It may also imply to why she was looking ill when Destiny Islands was devoured by the darkness before she disappeared.
In the manga, according to Axel, Kairi is able to travel through the Corridor of Darkness without any negative effects because she is a Princess of Heart.
Keyblade Wielding
Kairi's abilities in combat are limited. Kairi isn't able to do much when she is in danger, and frequently depends on Sora or Riku to come to her aid; this also results in her sometimes being captured, which is seen when Axel merely grabbed her by the wrist and dragged her along without any problems. During the events that take place in the World That Never Was, Riku hands her a Keyblade crafted from his memories of Destiny Islands, and allows her to wield it so that she may combat the Heartless. She is shown to be fairly competent with it, and was shown to take out several Heartless on her own in cut-scenes.
Kairi is able to wield the Keyblade due to her having touched Aqua's Keyblade many years earlier.

History
Kairi is one of several original characters appearing in Kingdom Hearts Birth by Sleep, Kingdom Hearts, Kingdom Hearts: Chain of Memories and Kingdom Hearts II, and also one of the main characters in the series. She is the original persona of Naminé. Kairi was born in Radiant Garden and currently lives on Destiny Islands along with her two best friends, Sora and Riku. She is four during Kingdom Hearts Birth By Sleep, fourteen at the start of Kingdom Hearts, and fifteen during Kingdom Hearts II. Kairi's name is derived from the Japanese word for "Sea".

So begins...
Kairi KH2 She walked in pushing the doors gently, and looked around casually. She went to a near by table and sat down thinking.
Kairi KH2 she walked in through the bar doors and made her way silently to a table, sitting down with a sigh, just thinking.
Kairi KH2 she looked over to Riku, "oh no, but i heard she'd be here soon" she said with a smile before noticing Sora, "Sora!" she exclaimed and stood up in her seat looking at him happily.
Kairi KH2 her eyes went wide slightly, but she hugged sora back happily still smiling as they departed from the hug "hehe it's fine! How have you been sora?"
Kairi KH2 Kairi answered interested "awesome! ooo really new heartless and world? Better be careful" she said with a giggle. she then froze as riku pushed sora into her.
Kairi KH2 her face went bright red, feeling embarrassed, "I u-uh um," she stuttered before looking at Riku "Riku!" she exclaimed in response to Sora's explanation. she then went wide eyed as Riku whispered those words into her ear. She was speechless.
Kairi KH2 "hehe Riku your such a liar, cheeky" she said giggling, before looking at Sora getting worked up. She patted his head softly with a smile and said "how about we all get ice cream? I'm so addicted to it"
Kairi KH2 "Riku!" she exclaimed at what he whispered. she then looked over to Sora and as she imagined him saying those things, it made her more and more red.
Kairi KH2 she froze as the words rushed around her head, she was speechless, still staring at sora, she felt stupid but she couldn't look away or move.
Kairi KH2 "D-d-drawings?" she stuttered, still staring at sora. she then shook her head still bright red. "Sorry Sora," she said awkwardly. she then looked around puzzled, "your such a liar Riku haha," she said giving a fake laugh.
Kairi KH2 she looked at the drawings blushing as her smile went all wiggly embarrassed "Y-you could of drawn them!" she said denying the truth.
Kairi KH2 "O-oh...um, your very good at d-drawing Sora..." she said looking away from the drawing.
Kairi KH2 "your welcome.." she said before trying to see what was in Riku's hand, but Sora snatched it away. "w-well this is awkward...what's in your hand Sora?" she questioned suspiciously.
Kairi KH2 she caught a glimpse of it, she new it was a soft material, cloth cotton could be anything.
Kairi KH2 "hmm....let me see." she said walking closer to Sora.
Kairi KH2 "Let me see Sor-" she was interrupted by Riku pushing her into Sora. She blushed, but then grinned evily and placed her hand in Sora's pocket pulling out her panties quickly.
Kairi KH2 "Sora!" she exclaimed, "How did you get these?" she grasped onto her panties tight, bright red, "A picture?" she questioned Riku.
Kairi KH2 she looked at the picture speechless, "Ah!!! No! Pervert!" she said squinting her eyes, embarrassed,
Kairi KH2 staring at Sora she questione "Reeeeeaaally? You promise?" she looked deep into his eyes, hoping to get a truthful answer, even if it was the same.