Total Concentration Breathing

Total Concentration Breathing (の) is an esoteric breathing technique used by Demon Slayers.

Overview
Total Concentration Breathing is a breathing technique which involves expanding one's lungs to intake as much air as possible, accelerating one's blood flow and heartbeat while increasing their inner body temperature, resulting in their bones and muscles becoming more excited.

Using Total Concentration Breathing essentially enhances the user's physical traits and capabilities while still remaining human. Such traits include superhuman strength, speed, stamina, durability, endurance, and the mental abilities needed to keep up with their superhuman bodies, such as a faster thought process and reaction time. Being more proficient in Total Concentration Breathing is key in raising one's survivability while fighting demons.
 * Strength: Users of Total Concentration Breathing gain superhuman physical strength, being able to perform feats such as slicing through boulders, generating huge gusts of wind with a single sword swing, effortlessly breaking a person's arm, shattering ribs, picking up and flinging another person with a single arm, launching a person tens of meters, and moving massive boulders with your bare hands.
 * Speed: Users of Total Concentration Breathing have the ability to move and travel at superhuman speeds, being able to easily move faster than the eye can see making it seem as if one teleported, cross great distances instantaneously, and evade extremely fast attacks such as sound or lightning.
 * Stamina & Endurance: Users of Total Concentration Breathing possess inhuman stamina and endurance. Users can remain active for prolonged periods of time without tiring out. Tanjiro Kamado has once lived through 7 days of extremely harsh training where he was constantly fighting and being physically wounded without food, sleep, and water only when it rained. During the Infinity Castle Arc, the Demon Slayers had to fend off Lower Rank-level demons and even face off Upper Ranks for around 5 hours before engaging in battle with Muzan Kibutsuji until sunrise.

Total Concentration: Constant
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. By doing it every minute of the day, one's physical fitness drastically improves.

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. When Tanjiro first heard of the constant technique, he thought it was impossible as he already found it extremely hard to just use the breathing technique for just a little and when he started practicing it for a longer period, he felt like dying. His lungs and head would hurt and his eardrums would pound, and for a second he was terrified that his heart was coming out of his ears.

The training process involves blowing into a special type of super durable dried 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.

To be able to improve Total Concentration Breathing and blow the gourd, the user should work on their lung power first. Tanjiro did this by getting up early and run around which works out his lungs with fast movements. He also practices holding his breath. Lastly, as meditation helps with concentration, he also meditates by sitting in a Siddhasana pose on the roof of the Butterfly Mansion, and breathing slowly and deeply circulating the air all the way to the fingertips. After fifteen days, he could run longer and his lungs have gotten stronger. Tanjiro also asked Naho Takada, Kiyo Terauchi and Sumi Nakahara to hit his covers with blanket beaters when he stops doing Total Concentration Breathing during his sleep. After ten more days, he managed to successfully maintain the breathing technique an entire day without stopping and was able blow the largest gourd.

Enhanced Recovery
At a more advanced level, Total Concentration Breathing is also capable of slowing down the circulation of poison in the bloodstream and even clotting wounds from severe injuries. By focusing on every inch of the body and raising the accuracy of one's Breathing, one can spread their sensitivity throughout one's body and detect and even heal hidden internal wounds they may have.

After Tanjiro Kamado was stabbed by the Train Engineer with an awl, Kyojuro Rengoku taught him to use the technique to detect the ruptured blood vessel in his stomach and then use hemostasis to stop the bleeding. 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.

Recovery Breathing
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 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.