Fans Speculate: What's the Meaning Behind Tanjiro's Scar? Shinjuro Rengoku's Answer
Warning: This Article Contains Spoilers for Episode 13 of Kimetsu no Yaiba Season 2 Anime.
Tanjiro's scar has become a controversial topic among fans in Kimetsu no Yaiba. In the Entertainment District arc, Shinjuro Rengoku, Kyojuro's father, answered one of the big questions in a humorous manner. Turns out, Tanjiro's scar on the forehead is linked to certain meanings, rather than just being a Todoroki mark caused by hot water scalding.

Tanjiro wasn't born with the scar. Instead, it only appeared after Tanjiro saved his younger brother from a mishap of dropping hot tea. At the beginning of the story, the scar is a faint pink circle on the forehead. What's noteworthy about the scar is that while it's not congenital, Tanjiro's father also had a similar mark in the same position on his forehead. However, his scar was never explicitly explained, leaving it as a mere coincidence not quite convincing.
After taking a direct hit to the head, Tanjiro bled and had to be bandaged in subsequent episodes. However, ultimately when the bandage was removed, Tanjiro's scar underwent a transformation. It turned rough, with a deep red hue. No one paid attention to this change throughout the series, with many viewers assuming it was just a graphical enhancement to make the character look cooler.

Tanjiro's Scar: Unveiling the Truth
Shinjuro Rengoku's Explanation: The Secret Behind Tanjiro's Scar

Supporting Evidence: The Mystery of Sun-Breathing