Longtime friend of Riku and Sora, and one of the Seven Princesses with ties to the Keys and Keyholes. Not long ago, when she was lost in the darkness, Riku and Sora both tried to save her, each in his own way.

Thanks to them, Kairi was able to return to her home islands, but her memories of Sora were gone, and she soon stopped visiting the island where they once played.

-- Kingdom Hearts II Entry 01

Personality:
“Sora, you lazy bum. I knew I’d find you snoozing down here.”

Kairi comes off as a spunky girl with a light sense of humor and a gentle heart. She clearly is not a physical fighter as demonstrated at Destiny Islands where she is the only member in her circle of friends who does not spar against Sora. She does, however, enjoy being an instigator for the playful rivalry between her closest friends, Sora and Riku. She loves to prod and poke fun at her friends with an endearing sense of humor.

Despite not being originally from the islands, Kairi isn’t one to brood over it. She does think of it from time to time out of curiosity, especially since her memories are vacant of any time before her life among the trio. However, Kairi seems to carry a philosophy of living in the now and enjoying life. She definitely isn’t one to mope. That’s no fun at all!

That isn’t to say that she isn’t bothered by anything though. Anything currently troubling her life gets her full attention and she’ll be more than willing to face it head on. Kairi isn’t one to back down. This same display of courage to face her problems is reflected even when she faces particularly dangerous situations. That’s not saying that she’s fearless. Deep down, she may be scared out of her wits. However, her stubbornness can tend to cap that outcry even when she’s facing adversaries that could very well be the end of her. This is shown in her protection of Sora when he’s a heartless.

Still, Kairi does have a side of insecurity. She hides it well for the most part, but here and there it shows. Most particularly when she gives Sora her charm and has him promise to bring it back. There was evident fear that she would lose her friends. And it’s a fear that she has carried ever since then. If Kairi were to ever lose her friends, it’s hard to say what she would do.

Surprisingly, despite all the hardships that Kairi has either heard of or seen take place, she remains a positive individual. Her enthusiasm is ridiculous. She is constantly optimistic, wearing a smile that’s contagious. Rather than just sympathize with someone, she will do her best to go out of her way to make someone happy again if she can. Argue that it’s the whole “Princess of Heart” spiel, but it’s really just her in a nutshell.

And, speaking of being a “Princess of Heart”, this new revelation hasn’t really affected Kairi very much. Kairi is, well, still Kairi. And as long as she has her friends, that’s all that really matters to her.

In recent, Kairi has become a little more withdrawn than her usual self would be. This has stemmed from her inability to remember Sora. She knows that he exists, but she just can't seem to place how or why. Her island friends, unfortunately, don't help her. They don't remember anything about another boy other than Riku and this further discourages her. Who is the other boy? He must have been important, she thinks.

Abilities:

As noted before, Kairi isn’t the fighting type. She never had an interest to be involved in sparring simply because it didn’t suit her tastes. Her true abilities all seem to connect to her affinity with light. Being a Princess of Heart, she has no darkness contained within her. Because of that, when she loses her heart, her body becomes nothing more than a lifeless puppet rather than transforming into a heartless. This also means that she would usually not possess a nobody. However, under an unusual account of circumstances, Naminé was "born".

The other side of being a Princess of Heart is that she serves as one of seven keys that opens the final keyhole in Hollow Bastion (later renamed Radiant Garden). It's never explained so far as to how she became a princess or how they are capable of accomplishing such a feat in the English dubbed games released so far. It can only be argued that it is because of her unique affinity with light.

Also, because of her connection with light, Kairi seems to be able to combat and see through the darkness. Most of this is proven through the other princesses as they try and hold back the darkness to give Sora and the others time to escape in Hollow Bastion. They also note that they can sense it, which Kairi probably can as well.

Multifandom Test:
Kairi could probably easily relate to Winry Rockbell from the first anime adaptation of Full Metal Alchemist. Both girls are continuously separated from their childhood friends. They feel a little left behind, but they try to make the most of things, regardless, and help in any way they can when the boys are around be it encouragement or automail repairs in Winry's case. Both of them also face the knowledge that things have really gone amiss in their lives. War broods in both of their worlds and their friends have suffered through tremendous changes that they want to fix. Despite this, they always carry a good sense of determination and willpower that both of them could relate to.

It would be entertaining to see these two have a conversation concerning their boy woes and how they both really wish they could be taken along for the ride. I'm sure they would have some embarrassing stories to exchange about their friends, too. ;D