Unlimited Blade Works is a high-class thaumaturgy that embodies the caster's internal world and imprints it upon the world as a bounded field. It serves as the embodiment of their soul, the result of "Sword" being both their Origin and their Elemental Affinity, and the basis of their chakra and memory-based perception skills. Koyoichi has no penalties from the world while utilizing his version of Unlimited Blade Works.
Koyoichi uses an incantation to facilitate the invocation of the Reality Marble. It is close to a "Ten-Count" aria, using a poem about the caster as the basis, used to activate high-thaumaturgy. Koyoichi describes it as a suggestion to change himself and the words that will "connect Ayime Koyoichi." The lines of the incantation can be said at any time without requiring preparation, and Koyoichi is able to speak casually in between them. The first line is often used in order to strengthen a projection, such as with Koyoichi's use of Kanshou and Bakuya. I am the Bone of my Sword
Steel is my Body and Fire is my Blood.
I have created over a Thousand Blades,
Unknown to Death,
Nor known to Life.
Have withstood Pain to create many Weapons
Yet those Hands will never hold Anything.
So, as I Pray--
Unlimited Blade Works!
Once the incantation has been completed, an illusionary fire that doesn't emit any heat spreads out to form a boundary and wall for the bounded field, indicating the technique was a success. The bright light fills the vision of those present, and manifests an open, barren desert, littered with countless swords anchored in the ground like grave markers in a waste yard. Monolithic black gears gyrate in the distance. Koyoichi's version has a thick haze formed from embers and wisps of black smog produced by iron forging rising from the ground to opaque the view. Its purpose is a steel manufacturing factory that produces the countless weapons and defensive armaments that extend into the horizon of the kingdom of rubble. It contains all of the raw materials needed for the formation of the weapons, and it records and analyzes all weapons and defensive armaments encountered. The number of unique weapons encountered and recorded by Koyoichi exceeds numerous thousands, although he's only ever seen utilizing his few favourites. Quite notably their entire histories, compositions, and designs are all perfectly recorded, allowing for instant proficiency with the weapons by inheriting all combat skills and techniques utilized by their original owners.
The basis for the world in the Reality Marble is a hill of swords that spreads infinitely in their minds. The reflection of this inner world depends on their state of mind and their experiences in life, which means that they are completely different and incompatible with each other. Koyoichi's is formed from the basis of having been betrayed by everything, including his own ideals, and in the end having only been granted this one single ability. The Reality Marble is able to invade Koyoichi's body in the form of numerous blades during severe trauma to heal and overwrite wounds. It changes the nature of his regeneration into a indirect form that “changes his muscles into blades in order to knit his wounds with swords.”Swords, spears, and halberds are favored, but shields and defensive armaments are also replicable at two or three times the chakra cost. Due to Koyoichi's origin being "Sword" of which serves as the symbol of his character, all information stored is limited to close combat weapons. Weapons encountered are immediately analyzed with a single glance, enabling them to be projected immediately afterward, and once projected, they are stored within the Reality Marble for later use. The analysis of weapons is limited only to the direct use of human senses, meaning that blueprints and materials will be unable to provide the necessary information for a proper analysis. The quality of projected weapons will always be degraded by one rank due to humans being unable to fully conceptualize the existence of an object through only one sense, and they will never equal the originals.
Without being deployed, the Reality Marble allows for projection and reinforcement in the real world. Weapons are produced within Unlimited Blade Works and then brought into the world, greatly lowering the cost of reproducing them and allowing for numerous weapons to be prepared at once to be projected. Weapons can be summoned directly to the user's hands, or they can be summoned to levitate within the air and fire upon the enemy as arrows like Manipulating Attack Blades. Once the Reality Marble is deployed, all of the weapons are available for use, and any weapon can immediately be called to the user's hands or levitated even while the user is in direct combat. The weapons reproduced once the Reality Marble is first activated will not consume chakra, but those used or destroyed within it will add to the cost of maintaining the bounded field. The amount of chakra used to reproduce weapons that did not exist after the bounded field was expanded and the amount of chakra used to recreate weapons destroyed while it is activated is very costly. Weapons can be summoned directly to the user's hands specifically through the utilization of Summoning: Lightning Blade Creation.
1. Reference (Technique Origin/Source)