Total Concentration Breathing

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

Overview
In order to use the breathing technique, the user needs to expand their lungs and inhale the maximum amount of oxygen into their blood within a specific breath pattern to raise their physical and mental prowess to their utmost limits. The breathing technique accelerates the user's blood flow and heart beat, and the inner temperature shoots up.

Superhuman abilities
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 Total Concentration Breathing can accomplish, and though it can't do everything, these things can help one become stronger than the day before.

Blood coagulation
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 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 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.

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.