Black coat

The black coat (黒いコート), also called the black cloak, is an article of clothing, imbued with magic, that protects the wearer's heart from the corrupting effects of traveling through the darkness between worlds. It was first used by Master Xehanort as an alternative to the traditional Keyblade Armor that shielded not only the wearer's heart but their entire being. 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 his Organization XIII and true Organization XIII, who use the corridors frequently. However, it also has been worn by Riku, Mickey Mouse, a Moogle peddling to the Organization, and Ansem the Wise when they find themselves in need of the corridors, as well as by Data-Riku, Data-Roxas, and the Heartless Mushroom XIII, Nightmare Anti Black Coat, Absent Silhouettes, and Organization XIII Replica Data which take forms mimicking the Organization members.

Development
The black coats were originally designed for Roxas and Riku in the secret video Another side, Another story... simply as a way to disguise them while they were still being designed for Kingdom Hearts II. It was again used simply to hide Xemnas's face during his optional boss battle in Kingdom Hearts Final Mix and in Deep Dive, starting the trend of all Organization members wearing it. Nomura stated in an interview that his initial idea for "The Gathering" was to have Terra, Aqua and Ventus wear similar coats to the Organization XIII coats to hide their at-the-time undesigned faces, but felt that he could not use black coats once again, and so chose armor instead.

Appearance
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 trenchcoat 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 heals. 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.

In the Kingdom Hearts II manga, the coat is depicted as capable of sustaining damage and being mended like any ordinary article of clothing.

Story
The first known use of the black coat was by Master Xehanort, who wears it when he travels from the Keyblade Graveyard in order to leave his comatose apprentice, Ventus, to expire at his boyhood home of the Destiny Islands. However, he frequently uses the corridors without wearing his coat.

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 path to assembling Xehanort's true Organization XIII to replace the initial version that had failed in the future. He is found and fought by Ventus, Terra, and their Keyblade Master friend Aqua when each of them returns, individually, to that world, but after being defeated he simply vanishes on his way further into the future.

Even later, after Terra-Xehanort became the Nobody Xemnas, his half-remembered recollections of his past led him to adopt the black coat as the uniform of his Organization XIII. Each member wears their coat throughout their service, as does the Moogle who purveys goods to their castle. 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.

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, assuming the identity of "DiZ", so that they are able to safely pass through Corridors of Darkness and evade the Organization. The pair wear their cloaks through multiple clashes with Organization XIII, 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 without his coat after receiving it.

Mickey eventually discards his coat when he rejoins Sora's group at the Battle of 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, then with a modified version of the coat featuring black thorns on a white background.

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 in fact Data-Roxas, who had manifested to protect Data-Sora from his hurt.

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.

At the same time, several of the former members of the Organization revive as humans back at 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. Even a solitary doppleganger of Riku who appears before Riku in the depths of Monstro wears the coat. In the final stages of their plot, the Organization places Sora under the influence of a Nightmare in order to prepare him as their 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.