Setting Kingdom Hearts Dark Road is set roughly 70 years prior to the events of
Kingdom Hearts Birth by Sleep. The story explores the origins of series antagonist
Xehanort, including his friendship with fellow Keyblade wielder
Eraqus and his growing fascination with the nature of darkness, which leads to the events of
Kingdom Hearts "Dark Seeker Saga". During the game, Xehanort visits several worlds based on Disney films, all of which were previously featured in
Kingdom Hearts χ, including Agrabah (
Aladdin);
Wonderland (
Alice in Wonderland); Dwarf Woodlands (
Snow White and the Seven Dwarfs); Beast's Castle (
Beauty and the Beast); and Olympus Coliseum (
Hercules). Scala ad Caelum, a world first seen in
Kingdom Hearts III, acts as a central hub for the characters in the story.
Story Xehanort, a teenager living bored on the Destiny Islands, is approached by Ansem, his
Heartless from the future, and is transported to Scala ad Caelum, a world where
Keyblade wielders are trained. Two years later, Xehanort — now a Keyblade wielder — and his classmates
Eraqus, Hermod,
Bragi, Urd, and Vor are told by their master, Odin, that seven upperclassmen have gone missing before their Mark of Mastery exam. Their fellow classmate Baldr has also left in search of his sister Hoder, who is one of the missing upperclassmen. Odin tasks the youths to explore the many worlds and find the missing students, reminding them not to interfere in the affairs of other worlds. Xehanort and his friends eventually find Vidar, Vala and Vali, three of the upperclassmen, who have been stealing items essential to worlds' natural order. Vidar explains that they learned of the thirteen incarnations of True Darkness from Odin, and that they now seek to purge the world of them by finding the seven pure lights needed to summon Kingdom Hearts. Realizing this could destroy the worlds, most of Xehanort's group opposes this, but a sympathetic Vor joins the upperclassmen. Baldr returns, revealing Hoder was killed protecting him, and suggests they go to the Underworld to find her and gain more information on Vidar's plan. While there, they find the souls of Hoder and her fellow upperclassmen — Heimdall, Helgi and Sigrun — learning that Vidar's desire to purge the darkness was to avenge their deaths.
Hades attempts to trap them all in the underworld, and the group is separated; only Xehanort and Eraqus are found and rescued by Odin. After they return, Scala ad Caelum comes under attack by Baldr, revealed to have been possessed by an incarnation of Darkness, which killed Hoder to make Baldr vulnerable to its possession. Baldr reveals he killed the other upperclassmen to trick the survivors into summoning Kingdom Hearts, with which he intends to consume the worlds in darkness; when the upperclassmen abandoned the plan, Baldr killed Urd, Bragi, and Hermod, planning to use all their deaths to summon Kingdom Hearts. Baldr kills Vidar, Vala, Vali and Vor before facing Xehanort and Eraqus in a final battle. With help from Odin and Hoder's spirit, Xehanort kills Baldr, destroying his Darkness in the process. As they mourn their friends, Odin decides to retire, planning to make Xehanort and Eraqus his successors. Unbeknownst to them, Bragi is alive, having secretly been possessed by
Luxu, and decides to keep watch over Xehanort. A year later, while preparing for his Mark of Mastery exam, Xehanort meets the
Master of Masters. Their conversation, combined with his own observations over the following years, leads Xehanort to believe that darkness lives in every heart, and that there must be balance between light and darkness to maintain the worlds' order. Eraqus rebukes him, believing only in the purity of light, and the two go their separate ways. Xehanort spends the next sixty years studying darkness, eventually reconnecting with Eraqus when he leaves his student
Ventus in Eraqus's care after extracting the True Darkness from Ventus's heart, which becomes
Vanitas. A
post-credits scene shows a flashback to Xehanort's childhood, in which he is watched over on Destiny Islands by his elderly mentor, a former Keyblade wielder who was reborn in a new vessel. The mentor believes Xehanort to be the "child of destiny", a prophesied savior of the world, and has sequestered him there to hide him from the True Darknesses until he becomes strong enough to defeat them. Years later, the mentor dies, content in having protected his friend
Ephemer's descendant. ==Development and release==