Extrasensory Perception

Extrasensory Perception is the supernatural ability to sense things that cannot be perceived by one's natural senses.

Overview
Extrasensory Perception (or ESP) grants the user a "sixth sense" which enables them to sense the paranormal or supernatural. In the world of Kimetsu no Yaiba, ESP is utilized by both Demon Slayers and demons in two ways: hyper awareness and combative clairvoyance. While never outright stated, there are two types of ESP: general ESP which demons and Demon Slayers alike possess and specialized ESP which come from supernatural abilities such as Blood Demon Arts. Generally, more refined ESP is associated with being a more capable and skilled combatant.

Auras function as a sort of beacon which demons and Demon Slayers can pick up through their ESP. The auras of extremely strong demons, such as the Upper Ranks of the Twelve Kizuki, can induce effects such as fear, shuddering, breathlessness, minor pain, and weakness. The aura of Muzan Kibutsuji could even crack glass in his surroundings when he was incensed.

Hyper Awareness
Users of ESP are more acutely aware of the entities in their surroundings through perceiving their presence (or aura), which allows them to pin-point their locations without needing to look at them.

Most Demon Slayers (particularly Hashira), are able to sense the presence of demons from an extreme distance. Muichiro Tokito describes demons as having strange aura, possibly being as to why their auras are so easily distinguished from that of humans. Kyojuro Rengoku describes Upper Ranks as having a heavy and overwhelming aura. Muzan himself states that skilled Demon Slayers such as the Hashira would be able to tell a demon's at work in Yoshiwara quite quickly.

While mostly speculative, demons appear to have sharper ESP, as Upper Ranks such as Kokushibo and Doma were able to tell Akaza died when they no longer detected his presence despite the two being extremely far away from Akaza. Moreover, Muzan Kibutsuji was able to pin-point the locations of all the Demon Slayers spread across an entire mountain and later, during the final battle, sensed that they were coming back to life and rejoining the battle. Additionally, Muzan mentioned that demons can discern humans by blood type, disease strains, and even their genes.

Combative Perception
ESP can also be used to great effect during combat, mainly through sensing an opponent's bloodlust and murderous intent. Through sensing bloodlust, users are more aware of when and where their opponent will attack, giving more time to prepare countermeasures.

Hashira such as Kyojuro Rengoku possess extremely heightened bloodlust perception, being able to detect the murderous intent of a girl trying to shatter his Spiritual Core while Kyojuro was asleep, and acted on instinct to prevent himself from being harmed.

Inosuke Hashibira developed a more powerful form of bloodlust sensing with the aid of his unnaturally sharp sense of touch, allowing him to feel where his opponent will strike as sharp pricks and stings at the area where they are looking at.

Through his Compass Needle, Akaza is able to detect something he calls "Fighting Spirit", which is essentially one's intent to fight and cause harm. Through this detection, Akaza can accurately discern where his opponent's are in his immediate surroundings, to the point of parrying surprise attacks outside his line of sight, and also pin-point where their weak points are. Moreover, he can also use Fighting Spirit as a means to measure how strong a being is at a glance like he did with Kyojuro, correctly identifying him as a Hashira.

Some Marked Demon Slayers can see into the Transparent World, a special form of ESP which enables them to see-through the skin of living beings. By seeing how their muscles contract and their blood-flow, users can also accurately predict where they are going to strike.

The only known way to stop exuding bloodlust and Fighting Spirit is by entering the Selfless State, a state of tranquility that erases one's presence from the battlefield entirely.