Kairi

Kairi is one of the central characters in the Kingdom Hearts universe. A childhood friend of Sora and Riku and a pure Princess of Heart. Kairi appears briefly in the third part of Disney vs. Non-Disney Villains War, not before she is disposed off the tournament.

Disney Vs Non Disney Villains War - Part Three
Kairi spends her time with Sora and Riku at the Destiny Islands. However, Maleficent manipulates Riku, as he unleashes his deeper darkness on the island, destroying all of it's living beings, including Kairi.

Disney Villains War 3
Though Kairi doesn't appear physically, she is mentioned by Riku, when the boy begs for forgiveness to his friends, as he transforms himself into Ansem the Seeker of Darkness.