|Spoiler Alert: This page contains spoilers. Read at your own risk.|
- Main Article: Shiba Tatsuya
Decomposition (分解魔法), rather than being any particular magic is the theory on which some of Tatsuya's innate magic spells work on, namely, Mist Dispersion, Gram Dispersion, Partial-Decomposition (Partial-Mist Dispersion). It is one of the inherent abilities Tatsuya [Destruction & Recreation] was born with. Decomposition describes his "Destruction" ability while Regrowth describes his ability of "Recreation". Note: Both of these abilities are associated with Shiva (Mahesvara), the Hindu Deity of Destruction & Recreation, thus was also used to describe Tatsuya by his enemies during the Okinawa Defense Navel Battle.
Decomposition, also referred to as Dissolution, Disintegration and "Demon Right", is one of Tatsuya's two innate active magic abilities along with Regrowth, relying on his innate talent to directly interfere with structural information. Using Decomposition, after identifying the design of any Eidos, Magic Sequence, or object, he can decompose the design. For physical objects, he can translate the physical object into signals, and then erase the base design at his leisure, breaking the inter-molecular bonds and so decomposing or disintegrating the target. For an information body (Magic Sequences), he can directly disassemble the design. Therefore, if used on a person, the parts that form the human body, including skin, flesh, nerves, body fluids, bones, and cellular structures are decomposed at a molecular level. This is one of the most difficult magic spells and part of the reason why Tatsuya is unable to freely wield Systematic-Type Magic; too much of his brain's Magic Calculation Area is dedicated to this ability and his other ability, Regrowth.
Tatsuya is incredibly skilled with this ability. He is able to cast his ability as a projectile, or an area of effect Decomposition magic to act as a defensive wall around him, and can focus it around portions of his body to act as a "sword," similar to the way in which Sonic Blade works. As a result, there are many "sub-types" of this spell; a few notable examples include: Mist Dispersion, Gram Dispersion, and Material Burst.
His skill displays not only in the existence of various sub-species of Decomposition, but also his mastery to control the scale. Besides the devastating large scale effects, he is capable of using it to dismantle mechanical devices like arms or locks, and with the help of Fujibayashi Kyouko he learnt to be able to use it to delete electronically recorded data too.
Decomposition is not unique to Tatsuya – there are other similar but high ranked spells that involve decomposition of matter and information – but no other magician in the past or present has been able to use decomposition to the degree that Tatsuya can.
Mist Dispersion (ミスト・ディスパージョン) is an undisputed A rank destructive Decomposition spell that directly decomposes the physical structure of the information targeted. It works on inanimate objects as well as living organisms. It can decompose muscles, tissue, bone, even organs into the basic molecules such as ions and the basic elements.
It is described as being considerably mundane and quiet. There is no sound or light emitted and when raised to the highest degree of Decomposition, even easily flammable materials will not ignite. The objects dissipate to dust, transform into steam and then scatter. This spell does not travel through physical space so it can be aimed through physical objects and is not limited by distance by any means.
Deep Mist Dispersion
Deep Mist Dispersion(ディープ・ミスト・ディスパージョン): A Decomposition Magic which decomposes substances into electrons, protons, and neutrons by interfering with the structures information of the substance deeper than that of Mist Dispersion. It was produced as a prototype in the development process of Baryon Lance, but Tatsuya thought that the burden is too great that it couldn't be used in combat.
Beta Trident(ベータ・トライデント, lit. Beta Decay Dispersion Trident) is a Decomposition Magic. A magic that decomposes matter into protons and neutrons and furthers neutron beta decay.
Material Burst (マテリアル・バースト) is the ultimate form of Decomposition Magic. It is a magic that can decompose matter into energy. This ability goes further than breaking matter down into its constituent molecules and atoms as it directly converts matter into energy. The resulting energy is released as both electromagnetic radiation and heat that expand and destroy the enemy.
Because this ability is so destructive and formidable, Tatsuya has unofficially been classified as a Strategic-Class Magician. Based on Einstein's formula  energy released through the decomposition of matter is the mass of the decomposed matter multiplied by the speed of light squared. As shown in the Yokohama Disturbance Arc, the energy released from one drop of water, a paltry 50 milligrams of matter, is equivalent to 1000 tons of TNT, enough to completely destroy a large ship. The energy released from a 1 kg flag was enough to destroy an entire naval base, a port, and a large fleet of warships.
Because of the nature of the spell, it has the potential to be the strongest of any Strategic level spell (the only thing necessary to cause a more destructive explosion is the conversion of even a bit more matter into energy).
There is no known counter for this spell. However, like most Strategic level spells, this spell must be fired from a distance with a highly specialized CAD if the caster doesn't want to die in the resulting explosion. The CAD that Tatsuya uses to cast this spell is Third Eye, which is usually locked up by the 101 Independent Magic-Equipped Battalion.
Gram Dispersion (術式解散) or Magic Dissolution is one of the two strongest counter magic spells (alongside Gram Demolition) within Non-Systematic Magic. This spell interferes with the casting of other magic spells by dissolving Magic Sequences.
Interestingly enough, like Decomposition, Gram Dispersion is not completely unique to Tatsuya, at least in theory. Any magician can technically cast Gram Dispersion as long as he or she can fully analyze the magic and then break it down into meaningless Psions before the spell is cast. However, this requires a full understanding of the spell being cast, something impossible in the era of Modern Magic. With the advent of CADs in the era of Modern Magic, leading to casting times of a fraction of a second, it is considered impossible to see and fully comprehend magic spells before they are cast.
Tatsuya, however, is able to use this because of his artificial magic processor and because of his other ability, Elemental Sight, both giving him the ability to fully understand spells during their invocation even before they are cast. Tatsuya's form of Gram Dispersion can be thought of as an extension of his Decomposition ability as it takes the target's Magic Sequence and fully decomposes it into a group of Psion particles without a meaningful structure.
Dissection is a variant of Decomposition Magic, which dissects the Psion Information Bodies, which are also known as Artificial Spirits.
Astral Dispersionis Tatsuya's new magic, which can work against Spirits (Information Bodies). It's a variation of one of his innate magic - Decomposition.