Birth by Sleep
Final Mix | 2.5
Terra, Aqua and Ventus are separated as Master Xehanort attempts to forge the χ-blade.
The story takes place ten years before Kingdom Hearts. Terra, Aqua and Ventus train under Master Eraqus in the Land of Departure. Terra and Aqua take their Mark of Mastery exam with Master Xehanort present. Aqua passes and becomes a Keyblade Master, but Terra fails because he cannot control the darkness in his heart.
When creatures known as the Unversed begin appearing across the worlds and Xehanort disappears, Eraqus sends Terra to investigate. Xehanort has encouraged Terra to use his darkness, and Terra hopes to prove that he can become a Master. A masked boy named Vanitas convinces Ventus to follow him. Aqua is then sent to bring Ventus home and watch over Terra.
The three travel through different worlds, fighting the Unversed and crossing paths with one another. However, Xehanort and Vanitas work to keep them separated. Xehanort manipulates Terra into relying on darkness, while Vanitas pushes Ventus to become stronger. The Unversed are revealed to come from Vanitas's negative emotions.
During their journeys, Terra meets Riku on Destiny Islands and performs a Keyblade inheritance ceremony, allowing him to become a wielder in the future. Aqua meets Kairi in Radiant Garden, where Kairi touches her Keyblade and also receives that ability.
It is revealed that years earlier, Xehanort split Ventus heart in two, one of pure light, and one of Darkness. It is revealed that the darkness removed from Ventus became Vanitas, and the light part was kept alive by a newborn Sora's light. Xehanort intends to force the two to clash and reunite, joining a heart of pure light with one of pure darkness to create the χ-blade. This weapon is the counterpart of Kingdom Hearts and can open the way to it. When Ventus tells Eraqus about the plan, Eraqus attempts to destroy him to prevent the weapon from being forged. Terra protects Ventus and fights his master, allowing Xehanort to strike Eraqus down and destroy the Land of Departure.
Terra, Aqua and Ventus reunite at the Keyblade Graveyard to confront Xehanort and Vanitas. Xehanort reveals that he intends to use Terra's body as his new vessel. He releases his heart and takes over Terra, becoming Terra-Xehanort (Terranort). Terra's will remains in his discarded armor as the Lingering Will, which fights back against him.
Meanwhile, Vanitas joins with Ventus and creates an incomplete χ-blade. Aqua and Mickey fight the possessed Ventus while Ventus confronts Vanitas within his own heart. They destroy the weapon, but Ventus's heart is damaged in the process. It finds refuge within Sora, leaving his body asleep.
Aqua returns Ventus to the Land of Departure and uses Eraqus's Keyblade to transform it into Castle Oblivion. She leaves him in the Chamber of Waking, hidden away in a place that only she can find. She then confronts Terranort in Radiant Garden, hoping to recover Terra. When he begins sinking into the Realm of Darkness, Aqua sends her armor and Keyblade to save him and becomes trapped there herself.
In the end, Terranort is found by Ansem the Wise and becomes his apprentice, leading to the events behind Kingdom Hearts. Terra remains possessed, Ventus sleeps in Castle Oblivion and Aqua wanders the Realm of Darkness.
Releases
| Release | Platforms | Date |
|---|---|---|
| Birth by Sleep | PSP | January 9, 2010 (JP) · September 7, 2010 (NA) · September 10, 2010 (PAL) |
| Final Mix | PSP | January 20, 2011 (JP) |
| 2.5 ReMIX | PS3 | October 2, 2014 (JP) · December 2, 2014 (NA) · December 5, 2014 (PAL) |
| 1.5+2.5 ReMIX | PS4 | March 9, 2017 (JP) · March 28, 2017 (NA) · March 31, 2017 (PAL) |
| 1.5+2.5 ReMIX | Xbox One | February 18, 2020 |
| 1.5+2.5 ReMIX | PC (Epic Games Store) | March 30, 2021 |
| 1.5+2.5 ReMIX | Nintendo Switch (cloud) | February 10, 2022 |
| 1.5+2.5 ReMIX | PC (Steam) | June 13, 2024 |
| Kingdom Hearts Collection [I~III] | PS5 · Xbox Series X|S · Nintendo Switch 2 · PC (Epic Games Store) · PC (Steam) | October 8, 2026 |