Kingdom Hearts 0.2 Birth by Sleep -A fragmentary passage-

Kingdom Hearts 0.2 Birth by Sleep -A fragmentary passage- is the ninth installment in the Kingdom Hearts series, and is included in Kingdom Hearts HD 2.8 Final Chapter Prologue. The game is rendered in and is exclusive to the PlayStation 4.

This game's story is an epilogue to Kingdom Hearts Birth by Sleep and a playable prologue to Kingdom Hearts III. It is connected to Kingdom Hearts χ and chronicles Aqua's continued journey through the Realm of Darkness.

Story
Luxu stands alone in the Keyblade Graveyard. With the No Name in-hand, he watches silently as Kingdom Hearts appears in the sky.

A century later, at the Mysterious Tower, Yen Sid tells Riku, Kairi, and King Mickey they must rescue Terra, Ventus, and Aqua. Mickey reveals he last saw Aqua in the Realm of Darkness:

''Aqua learns time does not flow in the Realm of Darkness by exploring the remnants of Castle of Dreams, and begins seeing silent illusory versions of Terra and Ventus. In the remains of Dwarf Woodlands, she defeats the Phantom Aqua, a ghostly copy of herself. In Enchanted Dominion, she catches up to Terra and Ventus again, and this time Terra responds, telling her the real him is lost in shadow. Suddenly, he is overtaken by Terra-Xehanort and she learns Xehanort is trying to find the Chamber of Waking, before the real Terra begins to fight back and confesses Xehanort is a part of him now.''

''While they struggle, Aqua is pulled deeper into the darkness, where she is found by King Mickey. The two Keyblade Masters team up to help Sora and Riku close the Door to Darkness so they can save the worlds from the Heartless. When the Demon Tide attempts to attack Riku, Aqua sacrifices herself to keep it at bay, vowing to act as a Wayfinder for anyone who falls into the darkness, and to return to her friends eventually. Later, on Destiny Islands, she watches as the worlds are restored; before being plunged even deeper into the darkness, where she finds Ansem the Wise at the Dark Margin.''

Having learned the role he unknowingly played in sealing Aqua's fate, Riku demands to know why King Mickey kept it secret. Yen Sid explains this was done to prevent Riku or Sora from attempting a doomed rescue of Aqua, then he reveals a safe means of entering the Realm of Darkness has been found. Riku and Mickey receive new garments made by Flora, Fauna, and Merryweather, and they depart to find Aqua and return her to the Realm of Light. Meanwhile, Kairi is instructed to train under the wizard Merlin so she can become a Keyblade wielder, although needs to be reassured when she hears her fellow pupil, Lea, was formerly Axel.

A short time later, Donald and Goofy reunite with Sora, who returns to Mysterious Tower after a prolonged absence. Sora is tasked with learning to retrieve lost hearts by Yen Sid, and he is told that almost becoming Master Xehanort's vessel has stripped him of many powers. Yen Sid reminds Sora of Hercules, who once lost and regained his godlike strength, and the Keyblade wielder departs with Donald and Goofy to pay the hero a visit.

Aboard the Gummi Ship, Sora and friends wonder how they will travel to other worlds, as the lanes between them have been resealed. Suddenly, Goofy remembers an old saying of Yen Sid's: "May your heart be your guiding key". Using his heart, Sora successfully opens a path to Olympus Coliseum.

Gameplay
Aqua controls similarly to her scenario in Birth by Sleep. Shotlocks return from Birth by Sleep, as does the Focus Gauge, although there is only one Shotlock, Prism Rain, and it must be unlocked near the beginning of the game.

The Command Deck from Birth by Sleep is gone and has been replaced by a Command Menu that acts more akin to Kingdom Hearts and Kingdom Hearts II, as the game is meant to prepare players for Kingdom Hearts III. The MP gauge returns and functions as it did in Kingdom Hearts II.

There are two shortcut menus. These can be scrolled through via. Magic and Items are listed separately.

Most of Aqua's Magic Commands from Birth by Sleep do not reappear, and she instead uses basic spells such as Firaga and Curaga, similar to Sora in Kingdom Hearts and Kingdom Hearts II. Blizzaga in particular can be used with Flowmotion in the form of Rail Slide.

When the player assumes control of Aqua, she starts off at level 50, and she will eventually be joined by King Mickey in the Depths of Darkness. Like Birth by Sleep, there are no Summons.

There is a new mechanic called Situation Commands. Command Styles return as a type of Situation Command but are now known as Style Change.

Once it is unlocked, Aqua can revisit locations by teleporting at Save Points. Due to the game's short play time which is only about 2 or 3 hours long, there are 51 Objectives to add replay value, which also unlock accessories and palette swaps to customize Aqua's appearance.

After clearing the game, 12 Zodiac Relics appear in scattered Treasured Chests throughout the entire game. Collecting them all unlocks a new mirror in The World Within which leads to a boss rush consisting of five rounds, the fifth being a harder Phantom Aqua.