Set directly after the events of the first Kingdom Hearts, Kingdom Hearts: Chain of Memories follows Sora, Donald and Goofy on their quest to find Riku and King Mickey, both of whom have been locked inside the Realm of Darkness, and the price they have to pay for achieving this goal. Beckoned by a hooded figure into the mysterious fortress of Castle Oblivion, the three friends begin ascending the castle's thirteen floors, unaware that the true meaning behind the line 'To find is to lose and to lose is to find' has begun to haunt them. There is no doubt that they will find people they miss, but would they be the ones they are looking for? If Sora, Donald and Goofy do not uncover the mystery behind the hooded figures tormenting them at every turn, this search might very well end in tragedy.

In the basements of Castle Oblivion, a young man haunted by the darkness of his past awakens....

Stranded in an unknown realm following the sealing of Kingdom Hearts, Sora, Donald and Goofy are intent on completing a mission to find the missing Riku and King Mickey, a mission which seems unlikely to ever be fulfilled. That is, until a hooded figure appears before them and shows them the pathway to a menacing castle.

"Along the road ahead lies something you need. However, in order to claim it, you must lose something that is dear to you."

Welcome to Castle Oblivion, where to find is to lose and to lose is to find. A place where you forget everything you have ever experienced, and yet memories can come alive. Spurred on by promises of a reunion with missing friends, Sora, Donald and Goofy begin a journey through illusions crafted from memories of the worlds they have visited, only to find out that what they are losing is their memories. Memories are closely linked to one's identity; surely if one loses his memories, one loses himself as well? Despite knowing full well that ascending the castle's thirteen floors means they lose thirteen floors' worth of memories, Sora, Donald and Goofy know that nothing can stand in the way between them and their missing friends, and that the important memories will always remain with them.

However, the more memories Sora loses, the clearer he remembers a young girl who was once a close friend of his, Riku's and Kairi's - Naminé, a girl who disappeared from his home when he was very little, and who now apparently is a hostage of the hooded figures lurking around Castle Oblivion, all of whom belong to an enigmatic intellectual group called the Organization. Bonds are tested when Naminé becomes an obssession for Sora, to the extent that she completely replaces Kairi in his memories. His desire to save his helpless friend drives a wedge between him, Donald and Goofy, and brings him into conflict with Riku, who as promised by the Organization, is reunited with Sora, but is sinking deep into darkness once more. But is Namine as helpless as she seem? And what of Axel, an Organization member who seems to be one step ahead of everyone, even his colleagues?

In the basements of Castle Oblivion, Riku awakens, only to find himself terrorized by Ansem Seeker of Darkness, the villian ofKingdom Hearts who has set his sights on possessing Riku once more. To this end, he continuously meddles with the darkness in Riku's heart, then convinces him to visit memory worlds which are only inhabited by creatures of darkness. As revealed by Ansem, this is Riku's fate for casting away his friends and home for power: Emptiness and eternity with beings who have the same lust for power as Riku himself does. Initially rejecting this punishment, Riku embarks on a journey to cleanse himself of the sins of his past, but soon discovers the futility of his efforts.

His path to self-discovery causes him to cross paths with the Organization and a heavily bandaged sage named DiZ, both of whom are determined to use him for their own plans. In addition, Riku's suppression of the darkness only makes it stronger, and him weaker to the light. Soon, when it matters most, Riku needs to make a choice: Will he allow himself to be consumed by light, or fade into darkness?

Betrayal, loss of identity and the never-ending conflict between light and darkness plague this intertwining tale of our two leading heroes' physical and internal journeys towards finding themselves. Truly, to find is to lose and to lose is to find.

Kingdom Hearts: Chain of Memories serves as a bridge between Kingdom Hearts and Kingdom Hearts II, exploring the events which led to Sora's year-long slumber and eventual awakening in Twilight Town. With Riku and King Mickey sealed behind the Door to Darkness, Sora, Donald and Goofy are drawn to a mysterious fortress named Castle Oblivion, where they are promised a reunion with long-lost friends, although this means they have to give up their memories in order to reach them. As the trio ascends the castle's thirteen floors, they find themselves being trapped in a complex web of lies and deceit orchestrated by the shadowy Organization XIII, the same villainous force that has been plaguing Riku's own search for redemption in the castle basements.

Following the sealing of Kingdom Hearts, Sora, Donald and Goofy are beckoned by a hooded figure towards Castle Oblivion, a place where cards reign supreme and where they are haunted by the phrase 'To find is to lose and to lose is to find'. Believing that ascending the castle's thirteen floors will promise a reunion with Riku and King Mickey, Sora and his friends begin a journey throughout illusion worlds crafted from the memories of their previous adventures. It soon becomes clear however, that what they are losing is their memories, but Sora is resolute in his mission, believing that the most important memories would never fade away.

As the layers of Sora's memories begin to peel, recollections of a young girl named Namine, a childhood friend of Sora's before she mysteriously disappeared from Destiny Islands, begin to emerge to the point that she completely replaces Kairi in Sora's heart. After several encounters with the malevolent members of Organization XIII, an intellectual group who seemed to be in control of the castle, Sora comes to the conclusion that Naminé is being held hostage, and it is his responsibility to save her. His concern for Namine soon becomes a fatal obsession which strains his friendship with Donald and Goofy. Riku meanwhile, appears to have descended into darkness once more and comes to a clash against Sora, believing that he alone can be Naminé's savior.

Neither Sora nor Riku are aware that they are being monitored by Marluxia, an Organization member and the lord of the castle, who is using the boys as pawns in an elaborate scheme to overthrow his superiors. Naminé is revealed to be a 'witch' with power over Sora's memories and those aligned with him, and has been forced to rewrite Sora's memories in an attempt to make him a puppet Marluxia can use. In addition, the Riku Sora has been fighting against is in fact a clone created by fellow Organization member, Vexen, in a plot to test Sora's strength.

Learning of Marluxia's betrayal of the Organization, Vexen attempts to warn Sora of the coming danger but is brutally cut short by Axel, a double agent who has no qualms about killing Vexen in order to infiltrate Marluxia's inner circle. Once Marluxia's back is turned, Axel convinces Naminé to seek a meeting with Sora and reveal the truth , effectively foiling Marluxia's plans. Although Sora now knows that his memories of Naminé are never real, he decides that his feelings for her are genuine. Drawing renewed courage from his friends and an alliance with the Riku Replica, he defeats Marluxia and frees Naminé from his hold forever. Axel, the only survivor of the Castle Oblivion massacre, is forced to flee to fight for another day, while the Riku Replica strives to forge a sense of identity for himself.

With thirteen floors' worth of memories gone, the only way Sora, Donald and Goofy can regain them is by sleeping in pods, although this means all events in Castle Oblivion would be forgotten. Sora and Naminé makes a promise to meet again once he wakes up, firmly believing that the important memories would never vanish, but instead lie deep in his heart.

Reverse-Rebirth

Running parallel to Sora's story, Reverse-Rebirth begins with Riku's arrival to Castle Oblivion, having been drawn to the place by Sora's presence. Rejecting a chance to hide from the sins of his past, Riku travels through various memory worlds, but encounters only darkness within. A reunion with an illusion version of Maleficent opens Riku's eyes to the consequences of his actions in Kingdom Hearts: His lust for the darkness had closed his heart off to the light, and all Riku would ever have for accompany are evil beings. Determined to make amends, Riku begins a desperate journey to decimate any dark beings he crosses paths with, unaware that by doing so he is actually trying to hide himself from his inner darkness.

Riku's redemption is interfered by Xehanort's Heartless, whose remnant lives on in Riku and is determined to possess the young boy once more. He tempts Riku into evil by awakening his dark potential, but fortunately Riku is constantly guided by a projection of King Mickey, who remains stuck within the Realm of Darkness. He is also being pursued by the underground members of Organization XIII: Vexen, Zexion and Lexeaus, all of whom intend to use Riku's darkness as a weapon against Marluxia. To this end, Vexen creates the Riku Replica, a clone of Riku who embraces the darkness, but is furious to learn that he is merely a copy with no real identity.

Walking the thin line between light and darkness proves difficult for Riku however, especially with Lexeaus attempting to draw out his inner darkness, an attempt which leads to the latter's death. Eventually, Riku arrives to Destiny Islands, where Zexion taps into his innermost fears and drowns him with light. Rather than fade into the light however, Riku takes advice from a memory version of Kairi: Accept both light and darkness, as both powers are neither good nor evil by nature. Embracing both halves of himself allows Riku to emerge victorious, and Zexion is murdered shortly after by Riku Replica on Axel's orders.

Riku is finally confronted by Riku Replica, the latter of whom is on an insane path to becoming the real Riku. The Replica is destroyed, and is forced to accept his fate as he fades into darkness. Shortly after, he is given a choice by an enigmatic sage named DiZ and Naminé: Naminé can seal Riku's darkness and with it, Xehanort's Heartless, but that means he has to sleep and lose his memories. Riku chooses to face Xehanort's Heartless alone, but not before realizing that both DiZ and Naminé were the ones who convinced him to embrace both light and darkness.

Riku makes a final stand against Xehanort's Heartless and wins the internal battle, although he knows that the villian's influence would always be inside him. With King Mickey as his companion, Riku is ready to join the war between light and darkness, not by walking the Road to Light, nor the Road to Darkness, but by the path less travelled: The Road to Dawn.