Created by Kokushibo back when he was a human, Moon Breathing is a Breathing Style used by Upper Rank One of Muzan Kibutsuji's Twelve Kizuki in Koyoharo Gotouge's Demon Slayer. Derived from Sun Breathing, the progenitor of all Breathing Styles, Moon Breathing evokes the movements of the moon, channeling the crescent-shaped forms it takes on at various points in the lunar cycle. Kokushibo initially developed it on discovering that he could not master Sun Breathing, back when he was a member of the Demon Slayer Corps, and he is the only known user of this Breathing Style till date. Its power was depicted to be so fearsome that Kokushibo could take on multiple Hashira at once and even gain the upper hand.
Although Kokushibo first used it as a human, the final incarnation of this Breathing Style cannot be performed by a human, owing to the fact that he combined it with his own Blood Demon Art. This allowed him to enhance his attacks to push beyond the limits of the human body, even with the aid of Total Concentration Breathing. Combining these two techniques proved to be a master stroke, as both Kokushibo's Breathing Style and his Blood Demon Art proved to work in perfect synthesis, making it one of the most fearsome abilities in Demon Slayer.
What Is Moon Breathing?
The shape of a traditionaly crescent moon serves as the foundation of this Breathing Style, which is firmly grounded in standard swordsmanship techniques, in keeping with Kokushibo's history in the Demon Slayer Corps. This bears similarities to Akaza's martial arts style Blood Demon Art, but is a stark contrast to the Blood Demon Arts of Gyokko, Hantengu, or Doma, whose abilities are a bit more conceptually or elementally rooted. Having failed to execute the techniques associated with Sun Breathing with the same degree of proficiency as his twin brother Yoriichi Tsugikuni, Michikatsu Tsugikuni — who became known as Kokushibo after turning into a demon — came up with his own alternative Breathing Style.
Following years spent honing Moon Breathing — both as a human and later, in tandem with his Blood Demon Art — Kokushibo perfected this fusion of the two techniques, which is the source of his immense power, netting him the position of Upper Rank One. All of the attacks that fall under the banner of Moon Breathing involve slashes and strikes that follow arcing crescent-shaped geometries, and release massive amounts of power, enough to take out multiple targets at once. He can make use of these techniques either with the base form of his katana, or the warped flesh katana which is its next evolved state. In this configuration his katana extends in length and takes on a branch-like appearance, with veins and eyes covering its blade and hilt.
Kokushibo's Blood Demon Art enhances these even further, releasing dozens of blades shaped like crescent moons — likely made from his own blood — whose shape, size, speed, and direction can be altered to strike targets from near impossible angles. This is one of the reasons behind why he is so powerful even among the Upper Ranks, as his attacks are not just powerful, but extremely erratic and unpredictable, such that his opponents cannot even read their trajectories, let alone evade, attack, or defend against them. He also does not need to swing his sword to release these blades, making it all more difficult to fight against him in single combat.
What Are The Various Moon Breathing Techniques?
Since Kokushibo has been alive for centuries as a demon, his use of Moon Breathing could be regarded as one of the finest forms of swordsmanship in Demon Slayer as a whole. At the time of the Infinity Castle Arc, he had developed a minimum of 16 Forms of this Breathing Style. The first among them, named "Dark Moon, Evening Palace," sees him unsheathe his sword and let out a single powerful slash, in the style of laijutsu, and then quickly resheath it again. This releases a single crescent shaped slash which also creates multiple smaller ones moving arbitrarily. Next, the Second Form of Moon Breathing, titled, "Pearl Flower Moongazing," involved Kokushibo releasing three crescent slashes which produce smaller, slashes in turn.
The Third Form, "Loathsome Moon, Chains," features a flood of small crescent moon blades created by Kokushibo performing two broad slashes immediately in front of him. "Moon Spirit Calamitous Eddy" is the name of the Fifth Form, which features a vortex of crescent moon blades, generated by layering long slashes over one another. Kokushibo can perform this technique without the aid of his sword, which makes it even more terrifying. The Sixth Form, "Perpetual Night, Lonely Moon - Incessant," unleashes a chaotic volley of curved slashes, with crescent moon blades than can destroy the surrounding environment.
"Mirror of Misfortune, Moonlit," makes use of his altered katana for the first time, and this Seventh Form of Moon Breathing consists of a singular frontal slash which releases straight and curved moon blades that expand outwards. The Eighth Form, "Moon-Dragon Ringtail," is a long range technique, where Kokushibo executes a massive slash which leaves a devastating trail of crescent moon blades in its wake. Christened "Waning Moonswaths," the Ninth Form comprises mutliple curved slashes that leave crescent moon blades in their path. Following this up as the Tenth Form, "Drilling Slashes, Moon Through Bamboo Leaves," comrpises three rotating circular slashes resembling saws, with crescent moon blades trailing behind them.
The Fourteenth Form generates an omni-directional vortex of slashes which expand outwards, unleashing waves of crescent moon blades, and is named "Catastrophe, Tenman Crescent Moon." Lastly, the Sixteenth Form — the last to be shown in Demon Slayer — has Kokushibo wing his altered katana upwards, resulting in six curved slashes crashing down in front of him with enough force to leave craters. On seeing the sheer diversity in how Kokushibo has applied his techniques alongside his Blood Demon Art, it is no stretch to say that he has become a master swordsman beyond compare, and only the power of Sun Breathing would be able to contend with him.