Demon Slayer is considered to be one of the modern Big Three shonen anime, alongside My Hero Academia and Jujutsu Kaisen. Any anime with such a global audience is guaranteed to have its fair share of fan theories, and Demon Slayer is no different. One popular theory demonstrates how five of the top Demon Slayer Corps members relates to the five senses.
This theory began early in the series, when five initiates passed the Demon Corps entrance exam. It's highly likely these members are closely related to the five senses, as they each have a heightened sense or power surrounding them. Tanjiro, Zenitsu, Inosuke, Genya and Kanao's character developments in the anime so far have allowed this theory to finally take shape.
Tanjiro Kamado: Smell
The first of the five senses introduced in Demon Slayer is the sense of smell, shown through protagonist Tanjiro Kamado. Tanjiro has a sense of smell that could rival a canine, being able to smell traps, blood, demons and even emotions. At various points in the anime, he is even able to visualize scents like mist in the air, following them as they pave the way.
Due to this being the first of the senses introduced, this could have been a simple character trait of Tanjiro's -- possibly a way of tracking demons. However, this theory grew more fruitful as more initiates and their respective talents were developed.
Zenitsu Agatsuma: Sound
The second sense was introduced with Zenitsu Agatsuma's entrance into the story. Zenitsu possesses enhanced hearing, allowing him to detect even the faintest of sounds, such as breathing, a heartbeat or blood circulating. He can hear movements from humans, animals or demons, and if he truly concentrates he is able to read people's thoughts.
This ability helps him locate demons who may be deeply hidden, sensing danger from miles away. It also makes Zenitsu quite musically gifted -- he can play a couple of string instruments, such as koto and shamisen.
Inosuke Hashibira: Touch
After growing up in the mountains and being raised by boars, Inosuke Hashibira developed a sharp and sensitive sense of touch. He is able to sense minute movements and feel vibrations through the air, which helps him track or locate disturbances.
This ability aids Inosuke in battle as he can sense when someone is looking at him -- especially if their intentions are hostile. It also helps him locate demons, as seen when he sensed Nezuko hidden in her box shortly after his introduction in Demon Slayer.
Kanao Tsuyuri: Sight
Kanao Tsuyuri introduces the sense of sight to Demon Slayer, as she has extremely sharp and accurate eyesight and notably large eyes. She can predict an opponent's next movement or attack by observing small changes in their muscles or joints and minuscule movement in their eyes.
The Breathing technique Kanao uses also enhances and utilizes the demon slayer's vision. At the possible cost of the user's eyesight, Flower Breathing can heighten one's sight in combat, and its final form allows the battle to be perceived in slow motion, giving more time to predict and plan attacks. When Kanao uses this form, her eye color and sense of sight both change.
Genya Shinazugawa: Taste
Due to its subtlety, this particular sense manifests differently from the others in Demon Slayer. Genya Shinazugawa is the most interesting initiate as he doesn't use typical breathing techniques. Instead, Genya carries a gun with bullets made of Scarlet Crimson Iron Sand and Scarlet Ore, which allows him to slay demons without a sword.
Genya can also temporarily gain demon attributes upon biting them and consuming their blood and cells. If he eats a particularly strong one, he adopts muscle and regenerative strength equal to that of a demon. While this representation of a sense is more subtle in context, there's no denying his ability has relation to the sense of taste.
While this Demon Slayer theory is compelling and appears to be more than a coincidence, the purpose of these five characters is yet to be fully revealed in the anime. It's possible the five senses will have to team up to defeat an overpowered opponent, such as Muzan, the main antagonist. Or maybe it's just an interesting quirk that creator Koyoharu Gotouge decided the give the five initiates. Future arcs may reveal the truth, but for now this theory remains a mystery.