Throughout the first and a half seasons of Demon Slayer: Kimetsu no Yaiba, viewers were divided and perplexed by Tanjiro's scar. Shinjuro Rengoku, father of the late Kyojuro, answered one of the anime's most burning questions for the second time in the "Entertainment District" arc. As it turned out, the scar on Tanjiro's forehead had a deeper meaning than just being a Todoroki-style burn from scorching water.

Tanjiro did not inherit this scar on his brow. He got it instead by tackling his younger brother out of the way of a falling pot of boiling tea. The scar was a light-pink, circular mark at the start of Demon Slayer. The only thing notable about his scar in the early days of the series was that, although being the result of an accident rather than a birthmark, Tanjiro's father had a nearly identical mark on his own forehead. Nonetheless, his father's scar was never addressed, and the series seemed willing to dismiss it as a coincidence.

 

What Caused Tanjiro's Scar to Change?

Demon Slayer: Tanjiro's Scar Has a Whole New Meaning_0

Tanjiro's scar didn't start to look strange until the Final Selection. Tanjiro's head was bloodied or bandaged for multiple episodes after receiving a hit directly where his scar is located. When he finally removed the bandages, the scar had turned to a jagged, dark-red line. No one in the series mentioned the alterations, so the viewers assumed it was just a retcon to make the mark seem cooler.

Fast forward to the "Entertainment District" storyline, and Tanjiro's scar is once again a popular topic of discussion. Tanjiro recalled a letter he received from Shinjuro Rengoku in the period since their first, unpleasant encounter during his combat with Daki, Upper-Rank Six of the Twelve Kizuki. Shinjuro appears to be the only one who knows anything about Sun-Breathing, and it is in this letter that he explains to Tanjiro that the scar is the mark of one chosen to use this technique.

 

Demon Slayer: Tanjiro's Scar Has a Whole New Meaning_1

Shinjuro claimed the mark was something people are born with, but Tanjiro was not. That alone would be enough to refute Shinjuro's claim. But when a memory from Muzan rises out of Daki's subconscious, it was a vision of a man wearing Hanafuda Earrings -- the symbol of Sun-Breathing -- and sporting a scar virtually identical to Tanjiro's. It is also noted that Tanjiro's father, who taught him the various forms of Sun-Breathing, was born with a scar on his head.

Ultimately, too much lined up for Shinjuro's claim to be anything but the truth. Sun-Breathing appears to be a thing of destiny rather than a Breathing Style anyone can learn. As the original, and most powerful, of all Breathing Styles, Sun-Breathing might just be the only thing capable of truly harming Muzan Kibutsuji and his most powerful demons. Judging by the visceral reaction of Muzan's cells to the memory brought on by Tanjiro's uncanny resemblance to the mysterious Sun-Breather, the Progenitor of Demons is not a fan of Sun-Breathing. All Tanjiro has to do now is stay alive long enough to master the Hinokami Kagura, because Muzan already wants no part of him even though Tanjiro can barely survive Sun-Breathing's full power.