The Demon Slayer Marks are mysterious, mystical scar-like markings that manifest in certain conditions on exceptionally strong Demon Slayers. Some of these conditions are as follow: 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 (102.2° Fahrenheit). The precondition in unlocking it is that an individual directly related to Sun Breathing is present with it. Once achieved, this mark can act as a catalyst and spread from the original user to other strong Demon Slayers through resonance. Achieving the Demon Slayer Mark grants the user the power of Bright Red Nichirin Sword, Enhanced Physical Capabilities, and Transparent World. These abilities enable them to become strong enough to fight Upper-Rank Class Demons on equal grounds. The side-effect of using the mark is an extreme strain on the user's body. Gyomei describes the curse's effect as "paying one's lifespan in advance in exchange for a greater physique." Furthermore, Demon Slayers who have awakened the Demon Slayer Mark might die upon reaching the age of 25 years old.