Breathing Styles

Breathing Styles are swordsmanship styles practiced and taught by members of the Demon Slayer Corps.

Overview
Breathing Styles are swordsmanship styles that makes use of an esoteric breathing technique known as Total Concentration Breathing (の) practiced and taught by members of the Demon Slayer Corps and are used in combat by Demon Slayers (later passed on as traditional dances post-time skip).

All known Breathing Styles currently taught within the Demon Slayer Corps are derived from Sun Breathing, the first one ever created. The majority of known Breathing Styles mimic a certain element of nature (i.e. flame, water and wind) and replicates it with the user's movements, techniques and abilities. The weapon attacks of Demon Slayers who use Breathing Styles are also longer ranged, possibly due to shockwaves or air pressure generated from their weapon itself when swinging and striking.

New Breathing Styles are always being created to suit a Demon Slayer's combat needs, which results in new weapons being utilized in demon hunting (i.e. flails and whips). Such Breathing Styles embody a bigger variety of concepts, like animals, plants and emotions (i.e. serpents, flowers and love). When utilizing a Breathing Style, users automatically visualize themselves manipulating the subject behind their style, making it seem as if they were using magic, though those that are less apt and proficient in their style will visualize less of it than one who is.

It is possible to mix different Breathing Styles if the user cannot master one particular Breathing Style alone in order to use the stronger aspects of different styles to compensate. Tanjiro, realizing that he could not master Water Breathing like Giyu Tomioka nor could he handle the strain of Hinokami Kagura, showed to be able to combine the two techniques together in order to have stronger strikes than when he used Water Breathing alone and move for longer periods of time than if he used Hinokami Kagura alone. He did this to save Hinatsuru from Gyutaro, and later used it once again during the Infinity Castle Arc to slay dozens of demons.

Total Concentration Breathing
Total Concentration Breathing (の) is an advanced and esoteric breathing technique where a user inhales the maximum amount of oxygen within a specific breath pattern to raise their physical and mental prowess to their utmost limits. The effects include a plethora of enhanced physical and mental abilities, like superhuman physical characteristics (i.e. strength, speed, stamina, durability and agility), faster thought processes, maximizing concentration and hyper-information processing. Kyojuro Rengoku notes that they are many things that a mastery of Breathing can accomplish, and though it can't do everything, these things can help one become stronger than the day before. At a more advanced level, Total Concentration is also capable of slowing down the circulation of poison in the bloodstream and even clotting wounds from severe injuries. By focusing and raising the accuracy of one's Breathing, one can spread their sensitivity throughout one's body and detect and even heal hidden wounds they may have such as the bleeding of a ruptured blood vessel. During his fight with Kokushibo, Sanemi Shinazugawa was, in addition to controlling his muscles to prevent his organs from falling out, able to stop his bleeding from multiple lethal wounds by using his Breathing to near-instantly coagulate his blood, a feat Kokushibo believes should not be possible for a human.

Tanjiro later showed another technique called Recovery Breathing, which, by taking a brief moment to focus and steady his breath, allows him to recover from fatigue and stiff muscles that prevent his body from moving after using Hinokami Kagura twice in a row. He used this after he had collapsed on the ground from using Hinokami Kagura to allow his body to move again and prevent himself from dying from Daki's attack. He later tried to perform it again to prevent himself from blacking out from exhaustion and lack of breath, but couldn't find a moment to do so due to the combined assault of Daki and Gyutaro.. Tanjiro Kamado displayed a technique called Recovery Breathing (の), which, by taking a brief moment to focus and steady his breath, allows him to recover from fatigue and stiff muscles that prevent his body from moving, which he uses to overcome the whiplash of using Hinokami Kagura techniques twice in a row.

Total Concentration: Constant (・) is a Total Concentration Breathing state during the morning, noon, and night, and even while asleep that advanced Demon Slayers, such as the Hashira, can constantly maintain. There is an immense difference in strength, speed, and stamina between someone who can maintain Total Concentration Breathing at all times and someone who cannot.

Learning to maintain a constant state of Total Concentration Breathing requires tremendous effort, though, the skill itself is noted to be quite elementary despite the required effort.

The training process involves blowing into a special type of super durable gourd. The objective is to blow into the gourd with enough strength to make the gourd break apart. As training progresses, the gourd is replaced by larger and larger variations of the same type of gourd. The largest known gourd is about the size of a chair.

Trivia

 * The names of Breathing Styles are very strict. For example, the Flame Breathing (の) should never be referred to as Fire Breathing (の).
 * According to the second fanbook, Breathing Styles were not entirely lost to history after the demons were wiped out. Instead, they eventually became traditional dances.