Black coat

The black coat (黒いコート), also called a "cloak", is an article of clothing imbued with magic that protects the wearer's heart from corruption when traveling through the darkness between worlds. Its abilities allow the wearer to use the corridors of darkness to quickly traverse the realms, and as such, it is primarily worn by Master Xehanort and the members of both the original Organization XIII and real Organization XIII. When denizens of light, such as Riku or Mickey Mouse, need to utilize the corridors of darkness, they also don the black coat.

Development
The black coat first appeared in the secret video Another side, Another story..., in which they were worn by Roxas and Riku. Xemnas also wore the coat in his optional battle with Sora and in the secret movie Deep Dive in Kingdom Hearts Final Mix. This started the trend of all members of Organization XIII wearing the coat. Tetsuya Nomura stated in an interview that his initial idea for "The Gathering" was to have Terra, Aqua, and Ventus wear similar coats to the black coat in order to mask their at-the-time undesigned faces. However, Nomura felt that he could not use the black coat again, and so he donned the trio of Keyblade wielders with armor instead.

Design
All black coats share the same basic design, although a coat often has unique personal touches and is able to change shape with its wearer. In addition, despite being put on and taken off as if it was just a coat, the coat actually manifests a matching set of pants, shoes, and gloves to replace any that their wearer was previously clothed in.

The main coat is a black leather trench coat that is double-breasted and twin-tailed, with a hood and long sleeves. It has a large silver zipper that fastens at the top and zips down to seal the coat. It has silver drawstrings for the hood decorated with a large silver bead hanging from the end and a silver chain ornament adorned with four large cylindrical silver beads that fastens to a loop on either side of the collarbone region.

Axel's black coat has narrow sleeves which stop at his palms, while Xigbar's has pleated shoulders and Demyx's has pointed shoulders. Larxene and Xion have coats with broad shoulders, and they come with boots that have narrow toes and prominent heels. Vexen's coat seems to be longer than most others, and his sleeves seem slightly longer as well. Roxas wears his coat with black sneakers, albeit of a different design from those he wears with his normal clothing. Mickey's coat is tailored for his unique frame, and they come with black versions of his signature shoes. Xion wears similar shoes when she takes Sora's form.

Kingdom Hearts χ
The first known use of the black coat is by the Master of Masters and his apprentice, Luxu.

Between Kingdom Hearts χ and Kingdom Hearts Birth by Sleep
Generations later, the Master of Masters gifts a black coat to the young Xehanort. He states that he doubts Xehanort will use it for long, as soon he'll be able to control darkness instead of needing protection from it.

64 years later, Master Xehanort wears it when he travels from the Keyblade Graveyard in order to leave his comatose apprentice, Ventus, to expire at his boyhood home, the Destiny Islands. However, he frequently uses the corridors without wearing his coat.

Kingdom Hearts Birth by Sleep
Years later, at the same time Master Xehanort attempts to reforge the χ-blade and take the Keyblade wielder Terra as his vessel, his time-traveling younger self arrives at the Land of Departure, wearing the black coat, on his quest to assemble Xehanort's true Organization XIII to replace the initial version that had failed in the future. He is found and fought by Terra, Ventus, and Aqua when each of them returns individually to his or her homeworld, but he vanishes further into the future upon defeat.

Between Kingdom Hearts Birth by Sleep and Kingdom Hearts II
Even later, after Terra-Xehanort becomes the Nobody Xemnas, his recollections of his past lead him to adapt the black coat as the uniform of his Organization XIII. Each member wears his or her coat throughout his or her service, as does the moogle who purveys goods to Organization's castle.

When Riku and King Mickey leave the Organization's former stronghold of Castle Oblivion, they are gifted with personalized black coats by the former king of the Radiant Garden, Ansem the Wise, who has assumed the identity of "DiZ", so that they are able to safely pass through corridors of darkness and evade the Organization.

The pair wears their cloaks during multiple clashes with Organization XIII, with Riku being labeled as the "Organization Imposter", culminating in the capture of Roxas at Dark City shortly after his desertion from the Organization. Roxas is placed within DiZ's simulated Twilight Town as a normal human, making him the first Organization member to be seen without his coat after receiving it.

Kingdom Hearts II
Mickey eventually discards his coat when he rejoins Sora's group during the Battle of the 1000 Heartless, while Riku continues to wear his until shortly after he rejoins his friends at The World That Never Was, when the explosion of Ansem the Wise's Kingdom Hearts Encoder returns him to his true form. When the group reaches Xemnas, the Superior replaces his black coat with his old Keyblade Armor, and finally with a modified version of the coat itself. The coat is also mimicked by a group of Heartless named the Mushroom XIII, who model themselves after the Organization, the Absent Silhouettes who manifest from the members' weapons after their destruction, and the Replica Data simulations housed at the Garden of Assemblage.

Kingdom Hearts coded
Shortly after the Organization's defeat, King Mickey digitizes Jiminy's Journal in order to determine the source of a mysterious message that had appeared within it. In the process, the Journal's collective memory comes to reside within Data-Riku, who takes the form of Riku as he was after he left Castle Oblivion, wearing a black coat. Because of his black coat, Data-Sora confuses him with the mysterious figure who appeared in his Dive to the Heart, but he eventually discovers that the figure was Data-Roxas, who had manifested to protect Data-Sora from his own pain.

Blank Points
Meanwhile, Aqua, trapped within the Realm of Darkness after her long-past battle with Master Xehanort, finds Ansem the Wise waiting at the Dark Margin in a black coat, having been cast there by the explosion of the Kingdom Hearts Encoder.

Kingdom Hearts 3D: Dream Drop Distance
At the same time, several of the former members of the Organization are revived as humans back in the Radiant Garden, and while most of them are wearing the lab coats or uniforms they wore when Terra-Xehanort transformed them into Nobodies, the human who had once been Axel, Lea, continues to wear his black coat as he leaves to seek Isa and assist Sora. Meanwhile, Young Xehanort arrives from the past with several of the members of the new, true Organization XIII composed of Xehanort's various incarnations. As they interfere with Sora and Riku's Mark of Mastery exam and maneuver Sora towards the gathering at Where Nothing Gathers, each of the members (bar Master Xehanort and Ansem) wear the coats symbolizing their allegiance; Ansem finally dons his coat at the meeting itself. In the final stages of its plot, the Organization places Sora under the influence of a Nightmare in order to prepare him as its thirteenth member. When Riku attempts to free Sora, the Nightmare manifests as the Anti Black Coat, a shadowy figure appropriately garbed in a black coat with a flesh-like violet tinge.

Kingdom Hearts III
Members of the real Organization XIII continue to wear black coats in the time leading up to the fated clash. Once the seven guardians of light and thirteen seekers of darkness have all been gathered and meet in the Keyblade Graveyard, all of the Organization except Master Xehanort appear wearing their black coats with their hoods up. Most of them maintain their coats through their individual battles. Lea also maintained his, rather than take a new outfit given to him by Merlin, noting the outfit's association with him as is.

Notes and references
Manteau noir