Riku Yami was born on April 17th, 1255 was a keybearer whoms adventures became legendary within the Malica Universe, he along with his friends and comrades reappeared in 1702 during the Colomar Outbreak, though evidence points to the Combine's involvement in his disappearance in and around 1274 NE.
- "I've always wondered why we're here on this island. If there are other worlds out there, why did we end up on this one? And... suppose there are other worlds... then that means ours is just a little piece of something much greater."
- -Riku, to Sora and Kairi
- In his adventures, Riku is a calm, cool, collected teen who is not afraid to go far beyond his limits. This shows through when he shows no fear in stepping into the dark portal when Destiny Islands is being consumed by darkness, along with his statement "I'm not afraid of the darkness!"
- He also showed a strong competitive streak, along with a bit of jealousy. He shows his competitive side when he challenges Sora, saying that his heart is stronger than Sora's heart. It is not actually said aloud, but thanks to Maleficent, he became increasingly jealous of Sora. It started with him finding out about Sora's new friends, and his thinking that he had been replaced. The jealousy grew when he learned about Sora possessing the Keyblade. The jealousy turned into rage, resulting in the battles against Sora throughout his adventures, and his possession by Ansem, Seeker of Darkness.
- Though his traits were not too favorable in his adventures, he becomes more heroic in his second adventure. Riku has many realizations. One of these was him realizing that he let his heart become weak, and realizing that surrendering himself to the darkness had only made him easily manipulated and controlled, not stronger. From that moment on, he began to shy away from the darkness in his heart. Through the scores of fights and battles in Castle Oblivion, he makes another big realization: he can't get rid of the darkness in his heart, and decides to use it without turning from the light like before. He matured immensely, and along with leaving his past behind him, he also left a lot of his unfortunate traits.
- Ever since he was young, he had been curious with everything that is outside of his world. Over time, his curiosity became an obsession and he began to think of his world as a prison surrounded by water. This obsession greatly diminishes throughout the year of Sora's slumber, most likely because he had already seen many other worlds that the curiosity disappeared. When he returns to Destiny Islands at the end of his third adventure, he still comments it as a small world, but agrees with Sora's remark that it is only a part of one that's much bigger. This marks that Riku has a better view of his homeworld rather than imagine it as a prison. Riku later stated that the real reason he wanted to see the outside was because of Terra.
Another good personality trait he showed is a strong protectiveness over his friends. He never wanted Sora and Kairi to find out about the time he spent in the darkness. He nearly sacrificed himself to protect Sora from Xemnas' attacks, leaving him injured after the final battle.
Though Riku matures significantly over the course of the series, he still seems to retain some of his old Kingdom Hearts self, particularly his sense of humor; he refers to Sora, Donald, and Goofy as "wise guys" when talking to the Emperor, cracks a joke about Donald and Goofy's intelligence at their expense ("Sora never did pick the brightest friends"), and calls Sora a "total sap" when going to confront Xemnas.
An important character development in Riku is noted by his change in haircut from having it extremely long in his third adventure, to returning it short again in fourth adventure. Riku's hair growth symbolized his loner ways and rebellion against his friends, but his cutting of it shows he now has trust and faith in both himself and them. He is now a hero instead of an anti-hero.