Kingdom Hearts χ Back Cover

Kingdom Hearts χ Back Cover is a feature-length, computer-animated film that serves as the tenth installment in the Kingdom Hearts series. It is part of Kingdom Hearts HD 2.8 Final Chapter Prologue and acts as a companion piece to Kingdom Hearts χ[chi]. The film is non-interactive and rendered with. It utilizes Kingdom Hearts III's Kingdom Shader.

Story
Long ago, in the "age of fairy tales," the world's light is protected by seven individuals who reside in Daybreak Town and wield unique weapons called "Keyblades": the Master of Masters and his six apprentices. A devastating conflict has been foreseen, and the world's end is imminent. In his discussion with one of his apprentices, Foreteller Ira, the Master of Masters states that the end of the world is inevitable. A desperate Ira insists that they should at least try to save the world, and believes that they might be able to do so with enough Keyblade wielders. The Master acquiesces to Ira's pleading, gives his disciples unique roles and instructs them to form Unions comprised of other Keyblade wielders. Soon afterwards, the Master vanishes.

Ira is left in charge of the other apprentices. Foreteller Invi is given the task of observing the other apprentices fairly, Foreteller Aced is tasked with supporting their leader Ira (a task that Aced reluctantly accepts, as it is no secret to the Master that he is eyeing the leadership for himself), Foreteller Ava is charged with preparing exceptional Keyblade wielders for the world to come, and Foreteller Gula is given the role of uncovering the mysteries of the Book of Prophecies. The last apprentice, Luxu, was tasked with watching his companions from a distance as they learned what they were meant to do.

One day, Ira discovers a dark Chirithy. This suggests someone has submitted to darkness and a traitor is present. Aced is the primary suspect, and it is soon discovered this was not foretold in the Book of Prophecies written by the Master, even though the latter had previously warned the Foretellers about the implications of the appearance of a dark Chirithy: if the rogue Chirithy is not stopped, it will plant darkness in the hearts of others, causing the appearance of a horde of Nightmares.

Aced convinces Gula to form an alliance with him so that they can fight the encroaching darkness together, even though alliances are forbidden. Gula makes clear that he does not want any of his Union members involved, and that the alliance is just between the two Foretellers. Ava witnesses this in horror, as this goes against the Master's teachings. Invi, whom Aced had invited to their meeting, has deepening suspicions of Aced after he explains to her that he wants to form an alliance.

Some time after this meeting, Ava sits alone at the Fountain Square, worried that the Foretellers might turn against each other. Ephemer joins her. Ava reminds him about a question he once asked her, about why the Unions compete against each other. Ephemer wonders if it is not simply because the Master said so, but Ava questions this, making reference to Ephemer's desire to solve the mysteries of this world. She expresses her belief that people should question things and think critically, leading Ephemer to remark that Ava is not herself. After trading jibes, Ava expresses how great it would be if all the Unions could work together and be friends. Ephemer tells her that he met a friend from another Union, and that they will meet again the next day. Ava tells Ephemer to go home and get some sleep, and Ephemer tells Ava to cheer up. Once she is left alone again, Ava thinks aloud, saying that she would be glad to leave the world in the hands of the children who see the world in the same way Ephemer does.

Back at the Foretellers' Chambers in the Clock Tower, Ira asks if Invi has learned anything. Invi replies, based on an assumption of hers, that Aced's and Gula's Unions are now allied. Ira believes that Aced is the traitor after all, but Invi disputes this, saying that to Aced, unification is a means of gathering strength to fight the darkness, and therefore, she believes that his heart still belongs to the light. Ira asserts that alliances are forbidden by the Master, and Invi agrees that the Master's teachings are absolute. As such, she expresses her will to try and persuade Gula to dissolve their alliance. Ira offers to do it in her stead, but Invi insists on doing it herself, as Ira's intervention will only serve to anger Aced even more. Before she leaves, Invi reveals that Aced has begun to question her proximity to Ira, and that as a precaution against Aced getting the wrong idea, her reports will be less frequent.

After a few months, Gula voluntarily dissolves his alliance with Aced, stating that the impending darkness he thought they were going to fight has not come, that there have not been any suspicious incidents of late, and that Aced has not rallied any newcomers to their cause. Gula sighs, saying that the alliance is meaningless and that "even Invi agrees." Aced questions Gula in anger, asking if Invi was the one who asked Gula to break their alliance. Gula denies this, saying that he himself decided to dissolve the alliance. Aced still insists upon the alliance, as they do not know who the traitor is yet, but Gula says that this is precisely why he decided to dissolve it — that he cannot trust anyone but himself. An enraged Aced asks Gula if he realises that he would not stand a chance against the darkness on his own, but Gula leaves, saying that his mind is made up. Still suspecting that Invi is the traitor despite Gula's words, Aced clashes with her, saying that it is time for him to fulfil his "true role." He disarms Invi and demands answers; Invi tells Aced that she is protecting the balance just as the Master had ordered her to do, and that he needs to come to his senses. Aced asserts that the apprentices need to defy the Master's teachings to protect the world, as he is no longer here. Invi and Aced violently clash again, while Gula looks on.

Ava rushes close by, and Gula calls her to the scene of the battle, where they both intervene. Invi tells Ava that she has found out who the traitor is, but Ava cannot believe it. Gula turns his Keyblade against Aced, and urges Ava to do the same, telling her that there is no time to lose. Ava reluctantly turns her Keyblade against Aced. Aced intones his Master's mantra, "May my heart be my guiding key," and battles the three Foretellers at the scene. The battle appears to have done considerable damage to a section of Daybreak Town, at least causing a bridge to collapse.

It is revealed that Gula possesses a Lost Page from the Book of Prophecies. Before his disappearance, the Master intended for Gula to keep hold of the Lost Page, which states that there is a traitor among the apprentices. The night following the battle between the Foretellers, Aced hides in a storage room to recover from the battle. Gula finds and approaches Aced, revealing the existence of the Lost Page. Stating that the Master had tasked him with finding and stopping the traitor, Gula points his Keyblade at Aced. Aced is enraged at Gula for having hidden that knowledge from him while the Foretellers fought each other, and proceeds to fight Gula. Gula protests, remarking that Aced can barely stand on his feet, but is nonetheless struck down by Aced. Ava, having heard the commotion, rushes to the scene and pleads with Aced to stop, putting herself between him and Gula as a human shield. Aced is upset that Ava has also seemingly turned against him, and stumbles out of the room, leaving her and Gula behind.

Aced is then accosted by Ira, but the two reconcile. Aced reveals the existence of the Lost Page to Ira, who then seeks out Gula in an attempt to see that Lost Page for himself. Meanwhile, Invi and Ava verbally clash about each other's recent actions, but stop and apologise to each other when Ava reveals that training Keyblade wielders separately from her Union is the role the Master assigned to her. Invi asks Ava what Ira wanted of her, but Ava simply says that she does not know. Ira just asked her to give up Gula without stating why. Ava remarked that Ira's eyes were "scary," and that she was afraid that he might do something terrible. Ava tells Invi that she sent Ira away; in reality, she had placed herself in front of Ira to shield Gula, just as she had done with Aced, prompting Ira to leave. Invi then asks after Gula, but Ava, who had been tending to his wounds, says that Gula has disappeared.

While Ava had been tending to Gula's wounds, she informed him that Ira wanted her to give Gula up. This prompted Gula to reveal his possession of the Lost Page. He told her that the page talks about "the one who bears the sigil," and that he did not know what to make of it. He regrets basing his actions on the Lost Page, as everything in the passage on that page is ambiguous at best. Desperate to find out the meainng of that page, he revealed his intention to summon Kingdom Hearts in order to lure the Master of Masters back to Daybreak Town. Ava failed in her attempts to dissuade him from doing so.

Realizing conflict between the Unions is inevitable, Ava acts in accordance with her role and gathers Keyblade wielders who must go into hiding instead of fighting, dubbing them the "Dandelions". Meanwhile, in the barren wasteland of the Keyblade Graveyard, Luxu pauses with the No Name and a mysterious box engraved with the phrase "χ Super", and intones his master's mantra, "May my heart be my guiding key."