The Kingdom Hearts series is home to one of the most bizarre stories in video game history. The first game followed Sora, a young island dweller, on a journey to reunite with his missing friends. It was a simple premise, but his adventure got complicated when his best friend, Riku, began relying on the darkness.
Each entry in the Kingdom Hearts series forces its protagonists to embark on a treacherous journey, on which they learn a great deal about both the world they live in, and themselves. Many of its characters evolve on their adventures, but certain characters' journeys have been a lot more compelling than others.
5 Aqua
The opening of Kingdom Hearts: Birth by Sleep saw Eraqus dubbing Aqua a Keyblade Master after the Mark of Mastery. Before she could celebrate her new title, she was tasked by her master to leave the Land of Departure, locate Ven, and escort him home. She learned a great deal about light and darkness on her quest, but nothing could have prepared her for what Xehanort planned to do.
Xehanort takes control of Terra's body, Ven's heart goes missing, and Aqua gets banished to the Realm of Darkness. None of these outcomes are ideal, but Aqua's is arguably worse. Not only does she get trapped in the Realm of Darkness; she is forced to wander its harrowing hallways for ten years until Sora eventually comes to save her. Though she remained a capable Keyblade Master after her rescue, she suffered a great deal of trauma during her time away from the Realm of Light, evident through how easily she accepted defeat at The Keyblade Graveyard in Kingdom Hearts 3. Since then, however, she has managed to regain her strength thanks to the help of her revived friends.
4 Sora
As the main protagonist of the Kingdom Hearts series, it would make sense for Sora to grow throughout each game he appears in. In Kingdom Hearts 1, his primary objective was to reunite with his missing friends, but he ended up getting roped into a much more sinister plot. Ansem was on a quest to plunge the Worlds into darkness, and though it wasn't Sora's job to stop him, he decided to do so anyway.
Since his first adventure, Sora has gone on to vanquish a variety of different forms of evil. He does so to ensure the World's survival, and also to guarantee the safety of his friends. The climax of Kingdom Hearts 3 saw him finally achieving all of these goals, but sadly, he didn't get to celebrate his victory. Instead, he was banished from the Worlds and sent to Quadratum, a fictional world about which very little is known. Sora's friends were always his power, but it seems he won't be able to rely on them in Kingdom Hearts 4.
3 Roxas
The opening of Kingdom Hearts 2 tells one of the most saddening stories in the entire Kingdom Hearts series. It follows Roxas and his friends during the last week of their summer vacation. Unless the player played Kingdom Hearts: Chain of Memories, they may not know much about Roxas' unfortunate life and why his time in Twilight Town is so bittersweet.
As Sora's Nobody, Roxas is doomed to fade back into Sora's heart. He tries to fight this destiny, but upon meeting Sora, he reluctantly accepts what fate has in store for him. Roxas tries to get his body back when Sora arrives at The World that Never Was, but sadly, he is unable to reclaim it. He accepts that Sora has more of a right to live than he does and gladly returns to his heart. It's a beautifully somber scene, and though it was a great end to his story, he eventually returned in Kingdom Hearts 3 thanks to one of Vexen's replicas. Though he accepted his fate in Kingdom Hearts 3, Sora refused to let his story end.
2 Xehanort
Xehanort was once nothing more than a villainous old man, hellbent on summoning Kingdom Hearts. Though his goal was unknown, it was assumed to be sinister due to the methods he used to achieve it. In Birth By Sleep, he murdered his closest friend, Eraqus, purely to hurt Terra, a young Keyblade wielder whose body Xehanort planned to possess. He ruined countless lives, but Kingdom Hearts: Dark Road revealed he had a good reason for what he did.
As a young boy, Xehanort was informed regularly by his guardian that he was destined to restore peace to the Worlds. It was because of this that he left Destiny Island and found himself studying to become a Keyblade Master. Unfortunately for him, the "Child of Destiny" prophecy was actually referring to Sora, but Xehanort only realized this by the end of Kingdom Hearts 3. By summoning Kingdom Hearts, Xehanort hoped to purge the Worlds, returning them to their original forms. He spent his whole life trying to achieve this, and only stopped his search when Eraqus confronted him from beyond the grave. Eraqus' kind words convinced Xehanort to end his search and accept defeat. In the end, Xehanort faded away with his old friend, permitting Sora to save the world himself.
1 Riku
Riku's debut in Kingdom Hearts 1, portrayed him as a relatively nice young man with an arrogant side. He, alongside his two best friends, Sora and Kairi, spent the better parts of their days playing together on Destiny Island. They lived a peaceful and carefree life until their home was consumed by darkness.
To rescue Kairi, Riku aligned himself with Maleficent and acted as her pawn for most of Kingdom Hearts 1. Through her, he gained the ability to control the heartless, a power that made him susceptible to Ansem's advances. Ansem took control of Riku's body because of the darkness in the latter's heart, banishing the young boy to the Realm of Darkness. Since Ansem's possession, Riku has become an entirely new character. He spent a great deal of time trying to deny the darkness in his heart, but he eventually came to embrace it in Kingdom Hearts: Chain of Memories. Since then, he has returned to Sora's side on countless occasions, not as an enemy, but as a friend.