Tanjiro Kamado, the protagonist of Demon Slayer, stands out as a compassionate and forgiving young man who has survived countless horrors during the Taisho era, a time of demons and slaughter. Given everything he's been through, the rugged Tanjiro appears older than his age, which has some anime fans wondering how old this tough shonen hero really is.
Tanjiro had to grow up quickly in order to become a powerful demon slayer and hero, but he's still a child by most people's standards. Tanjiro's youth distinguishes him as more than a typical shonen protagonist; it's also a commentary on how dangerous a career in demon slaying can be, and no demon slayer ever retires of old age.
Tanjiro's Age as the Shonen Protagonist of Demon Slayer
When Demon Slayer's story begins in Chapter/Episode 1, Tanjiro Kamado is 13 years old, which is younger than usual for many shonen heroes. While shonen is geared toward tween and teen boys, shonen protagonists tend to be 14 to 17 years old when the story starts, a relatable age for the target audience. Tanjiro is barely a teenager when Demon Slayer starts, which makes him even more vulnerable and naive than most shonen heroes are. Even in My Hero Academia's first episode, when Izuku Midoriya is still in middle school, he is 14 years old -- the same age as Iruma-kun!'s own youthful hero, Iruma Suzuki. This means that in Demon Slayer's first episode, "Cruelty," Tanjiro's sister Nezuko is even younger at age 12 or so.
Tanjiro didn't stay 13 for long, though. Once Nezuko stabilized as a demon who refused to harm humans, Tanjiro resolved to undergo demon slayer training and find a cure, which led him to Sakonji Urokodaki in the mountains. Tanjiro trained for two whole years in a training montage, which took place unusually early by shonen standards. Shonen heroes like Naruto Uzumaki and Monkey D. Luffy all underwent training arcs and returned older and stronger, and Tanjiro got that out of the way up front.
This means that Tanjiro is a more conventional age during the bulk of Demon Slayer's story, at age 15. That's a classic age for shonen heroes like him, with Izuku being 15 when he first enrolled at UA and Bleach's Ichigo Kurosaki being 15 when he first gained the powers of a Soul Reaper. Tanjiro's friends, Zenitsu and Inosuke are the same age and, notably, the elite Hashira are only a few years older than that. Demon slayers are all talented youths, but there are dark reasons for that.
Demon Slayers Have a Short Life Expectancy
A person's lifespan is an estimation of how long they may live in good health, barring accidents like fatal injuries or diseases, and humanity's lifespan actually doesn't change that much from one era to another. By contrast, life expectancy is the statistical average of how long certain kinds of people are expected to live, with lethal factors like war, disease, drug overdose rates, deaths in infancy and homicide lowering a community's or demographic's life expectancy. In theory, any demon slayer could live to old age and last as long as any Taisho-era citizen, but their deadly lifestyle means that their life expectancy is well under 30.
It's a concerning sign that the majority of demon slayers are in their late teens to mid-20s, with some Hasira barely old enough to drink. Even the most powerful demon slayers die within a few years or a decade of their careers, and it's likely that the Hashira are frequently rotated in and out as members are killed in action or forced to retire due to injuries. Tengen Uzui, the flame Hashira, died at the age of 23, while Kyojuro Rengoku died at the age of 20, and they were truly incredible demon slayers who vastly outclassed Tanjiro's squad in combat. If they die or retire at such a young age, Tanjiro and his friends may not live long.
Tanjiro beginning training at the age of 13 and becoming a proper demon slayer at the age of 15 is most likely the norm in Taisho-era Japan, and strong youths like him, Zenitsu, and Inosuke don't have time to waste. Demon slayers fight early and frequently, burn brightly, and die young the majority of the time. This is what distinguishes Demon Slayer's young heroes from Jujutsu Kaisen's teenage sorcerers or My Hero Academia's teenage hero students, neither of whom are expected to die so young. Tanjiro is only 15, but in his world, that is his prime time, and he must make the most of it or die trying.