Demon Slayer Mark

The Demon Slayer Mark is a mysterious marking that can be unlocked and may appear on the body of a strong Demon Slayer.

It resembles the Demon Crests that Demons possess.

It looks somewhat like a tattoo, scar, or birthmark and each Demon Slayer Mark looks unique, related to the Breath Style of the bearer.

Overview
A select few in the Demon Slayer Corps have developed a mysterious tattoo-like marking that can be unlocked and may appear on the body of a strong Demon Slayer. It resembles the Demon Crests that Demons posses. These marks are referred to as Demon Slayer Marks. It looks somewhat like a tattoo, scar, or birthmark and each Demon Slayer Mark looks unique, relating to the Breath Style of the bearer.

The true origin of the Demon Slayer Mark is unknown, however, the first recorded occurrence of these markings were in the Sengoku Era, possessed by the first person with a Demon Slayer Mark was none other than the first Breath Style user, Yoriichi Tsugikuni, who, for unknown reasons, was born with a Demon Slayer Mark. A handful of swordsmen who practiced the Breath of the Sun technique were also able to unlock the Mark around that time.

It is said that the Demon Slayer Mark has resonated since then and has been awakened by other Demon Slayers, which would later lay the foundation for the "Golden Era" of the Demon Slayer Corps, a time when the Demon Slayers came within inches of killing Muzan Kibutsuji.

Demon Slayer Marks disappeared for a long time, due to the countless times the Demon Slayer Corps was nearly annihilated, until it reappeared on Tanjiro Kamado, and subsequently, the Hashira who resonated with his mark.

Unlocking
The Demon Slayer Mark can only appear in Demon Slayers that survived the life-threatening conditions of having a heart rate over 200 bpm and a body temperature over 39° Celsius. The precondition in unlocking it is that an individual directly related to the Breath of the Sun has been born with it.

The Demon Slayer's mark also has the ability to act as a catalyst, and spread from the original user to other strong Slayers, such as the Hashira, through resonance, granting them Demon Slayer Marks of their own.

Abilities
The Demon Slayer Mark grants the user a number of abilities that are very advantageous in battle, especially against Demons.


 * Enhanced Physical Capabilities: Upon activating the Mark, the user is granted superhuman strength, speed, and enhanced breathing techniques beyond that of a normal Breath Style user. Their strength and speed could even rival that of the strongest Demons, such as the Upper Moons of the Twelve Demon Moons.


 * See-Through World: The user becomes able to see the muscles, blood flow, and joint movement of living beings, allowing the user to accurately predict and react to their opponents movements, as well as confirm the health and well-being of others. Additionally, the user gains hyper-perception, allowing them to perceive the world around them at a much fast rate, making it appear to them as if the world was going in slow motion.


 * Crimson Red Nichirin Blade: Demon Slayer Marks may enable the users to dye their Nichirin Blade in a crimson red color, giving their blades the ability to hamper the enhanced regeneration of demons.

Curse of the Mark
Having the Demon Slayer Mark has its costs. Demon Slayers who have awakened the Demon Slayer Mark are said to die upon reaching the age of 25. Kokushibo speculated this to be because the mark exchanged the life span of its user for power.

There are ways to avoid dying through the curse, as shown by Yoriichi and Kokushibo. Through unknown means, Yoriichi was able to defy fate and lived to be 85 years old, while Kokushibo chose to become near-immortal by becoming a Demon.

Notably, all records of users of the Mark dying at the age of 25 are of much older era than present times, which means this could merely be a superstition, as many Demon Slayers die at a young age because of their dangerous line of work. Notably, the power of the Mark, while immense, doesn't nesasarily guarantee the user will win every single fight.