Fans have always been so keen on every detail about the characters from their favorite story, be it the personality, plot, or character design. As such, Tanjiro’s scar on the left side of his forehead has always been a subject of interest for fans.
In the early part of the story, there is nothing particularly odd about this scar. One will just wonder how’d he get it and just move on with their life. But as the story progresses, this scar suddenly changes into something akin to a tattoo. It seems like it has developed and now represents something. It made the fans think that it isn’t just your ordinary tattoo but something that will play an essential part in the story later. So let’s explore every detail about this scar.
How Did Tanjiro Get His Scar? 2 Popular Fan Theories
From the beginning of the story, our protagonist, Tanjiro Kamado, has this scar on his forehead. It isn’t that important at first, but after the sudden change, it turns into something extraordinary. It turns into something. Before the actual revelation from the manga, fans have been theorizing stories surrounding Tanjiro’s scar on his forehead. These are the two most popular theories.
It isn’t a scar but a birthmark.

According to the first theory, the scar on his forehead is actually a birthmark. He always had this mark since birth, and since Tanjiro is the eldest, all his siblings grew up seeing this peculiar patch of skin on his forehead, thinking it was all normal. Unfortunately, there is no mirror in their home, and no one’s making a deal with this mark, so when someone asks where’d he get that scar from, he becomes curious and asks his mother about it.
To satisfy a kid’s curiosity, her mother conveniently told him he got it when he tried to save his brother from a falling kettle filled with boiling water. And the funny part is that due to a lot of headbutting he did to everyone, he has developed a scene in his imagination where he saves his brother from the kettle.
It is hereditary.
In Episode 19 of the anime, Tanjiro’s father debuted in his memory. Tanjuro also has the same scar in the same place. Because of this, the fans theorized that the Kamado Family’s eldest male is always born with a scar on the forehead. It will start as a tiny mark that looks like a scar and grow more prominent as time passes. And it is not just a simple scar but something more passed down through generations.

According to the letter written by Rengoku, the Sun Breath’s User has the same birthmark as Tanjiro. But the 15-year-old dismissed it by saying he got the scar when he was young, and that his father had a birthmark on the very same spot was just a coincidence. Tanjiro claims that he is not one of those chosen users. But that is just merely his humble stance.
The mark is the symbol of the Sun Breath’s User, and Tanjiro doesn’t believe he is something special. Despite what Tanjiro believes, the Sun Breathing Technique has something to do with the Kagura Dance that is passed down through generations of Kamado Family.
These two fan theories from even before the actual revelation really make sense, but how did Tanjiro actually get his scar?
What Does Tanjiro Say About His Scar?
According to him, the scar is a burn mark he got from protecting his brother from boiling water. It got wounded worse during the Final Selection Exam, making it look like what it is now. In the case of his father, Tanjuro was born with a small birthmark on the same spot as his, and it is just a coincidence. So, the theory that the birthmark is hereditary is proved wrong, if Tanjiro is right.

During the Final Selection Exam, Tanjiro had a life-and-death situation that he’d never experienced before. In that situation, Tanjiro’s body temperature reached around 39°. Meanwhile, his heart rate went over 200 beats per minute, which is precisely the critical condition for one Demon Slayer to manifest his or her Demon Slayer Mark.
Tanjiro awakens his mark that manifests in the left side of forehead overlapping with his previously scarred spot. It just so happens that the mark’s manifestation spot is the very same spot where his scar is located. That scar is wounded again during the Final Selection Exam, so he concluded that the changes in his scar is due to another wound on top of his scar.
When Did Tanjiro Get His Scar?
The earliest display of his scars from the anime is when he was still a child, so he was either born with it or got it when he was still a toddler.
Why Does Tanjiro’s Scar Change Over Time?
Throughout the entire series of Demon Slayer, one of the most talked about topics is the sudden change of the seemingly ordinary scar on his forehead into something of a mark that looks like a demon crest. This is due to the awakening of his Demon Slayer Mark. The mark manifests in a form of a deep red mark whose location depends on what kind of Breathing Technique one Demon Slayer uses.

Tanjiro’s Scar Evolution
The scar was originally just a patch of pink skin when he was young. It stays the same until his mid-teens. According to Tanjiro in Episode 6 of the Entertainment District Arc, he got it when he was still a child as he tackled his little brother to save him from a falling kettle full of boiling water.
During the Final Selection Exam, Tanjiro got another wound on top of his scar as he hit his head against a tree when he was flung after taking a solid hit in his body. His scar is gauzed for a few episodes and after taking it off, the former scar turns into a jagged deep red mark like a tattoo. Some part of the former scar that doesn’t overlap with the new mark returns to perfectly normal skin.
What Does Tanjiro’s Scar on the Left Side of His Forehead Symbolize?
The evolved form of Tanjiro’s scar, the mark that looks like a deep red jagged tattoo, is actually a Demon Slayer Mark. Some users of the first breath, who is one step away from killing Muzan Kibutsuji possess, this mark. Unfortunately, the mark has been lost through centuries among the Demon Slayers because the information has never been laid down accurately. So, the information becomes hazy with time or the Demon Slayers have been on the verge of extinction numerous times in the past. The mark differs depending on the type of breathing technique a person has.

In the case of Tanjiro, he has been obviously practicing the Dance of the Fire God or the Sun Breathing-turned-into dance through his father-to-son family tradition wherein the eldest male member of the family will dance the twelve segments of the Kagura Dance throughout the night until dawn. The Sun Breathing user manifests their Demon Slayer Mark on the left side of their forehead. It just so happens Tanjiro has a scar on the exact same spot that the Demon Slayer Mark is expected to manifest so when Tanjiro manifests the mark, it overlaps with the scar thus replacing it in the process.