|“||Piling one sin over another...the thing that awaits you at the end is 'Madness Release'...whether one can withstand it or not is a matter of your soul's worthiness.||”|
—The Index, Chapter 73
Madness Release (発狂, Hakkyou) is a technique characterized by the selective integration and application of a finite and limited quantity of the dangerous condition of madness into a person's respective soul, altering the quality of their Soul Wavelengths ordinarily emitted to contain instead the intended and permitted amount of insanity in addition. Undertaking this perilous process allows the user to manipulate the advantageous power-inducing attribute displayed by madness itself, granting them access to superhuman levels of physical prowess and their typical abilities. The madness in them is strong enough to even change their appearance. Each user of Madness Release has a unique variant of madness inside them, and although they utilize this madness and become, in a sense, 'insane,' they do not completely lose their sanity as they have a firm conviction that prevents them from doing so.
However, this technique does not come without risk, as the capability poses the significant potential of resulting in the individual becoming consumed by the very emotion they desire to exploit, losing themselves in the depths of madness and committing atrocities they would never normally consider. Certain steps can be undertaken to reduce or even negate this threat, such as the prior exposure and subsequent conquering of madness on a prior occasion or, through a Chain Resonance with an individual who demonstrates an great level of courage and an Anti-Demon Wavelength.
Death the Kid
Death the Kid's particular variant of this technique utilizes the madness inside him, the 'Madness of Order,' the desire for order raised to the very extremes. This is prominently featured within his distinctive personality. At first, Kid is overwhelmed by this madness and is bent on creating a world of 'nothingness' which surpasses all ideas of symmetry and balance. However, this is eventually overcome by the conclusion that ultimate order can only be achieved when there exists a harmonious coexistence between all things or, expressed in simpler terms, a 'balance,' and Kid is finally able to use Madness Release without losing his sanity.
While the ability is in effect, Kid's attire alters drastically due to the addition of a long-sleeved black shirt in the place of his current clothing, which is adorned by the presence of three horizontal white stripes equally distributed along the entirety of the tops length, and accompanied by a simple ruffled cravat worn around the neck. Some of the Lines of Sanzu he has also connect, and he is able to unleash a greater amount of power within them. Death the Kid describes his insanity as a 'cool killing intent.'
In regards to Black☆Star's experiences with this technique, it is instead dominated by his obsession to become an existence greater than a God and thus, is known as the 'Madness of Power,' derived from this selfish ideal. Although at first driven by the desire to become the most powerful being in existence, Black☆Star soon sees his desire to grow stronger as a means of achieving righteous or just goals, such as protecting his friends, and helping Kid create the perfect world of balance. Through this, Black☆Star is capable of changing this evident weakness into a notable strength.
When undergoing the release in question, his usual white and blue Spartoi uniform, including its characteristic scarf, darkens greatly in contrast to its typical appearance. Also, the numerous bandages that line his lower arms and legs become bisected by various black lines and his star-shaped pupils enlarge to point that they almost completely block out their respective irises. Whilst using Madness Release, he has access to strong attacks and superhuman strength, shown when he lifts the Cyclops with one hand.