Summary

• Tanjiro's scar is not just a scar, but a Demon Slayer Mark that denotes significant power.
• The scar changes and becomes a mark after Tanjiro's battle with the Hand Demon, indicating a transformation.
• The mark can be inherited and appears under specific superhuman circumstances, such as high heart rate and body temperature.

Warning: Contains SPOILERS for Demon Slayer's Anime and MangaDemon Slayer presents a subtle question to viewers in the form of what seems to be a scar on Tanjiro's head, which transforms in season 1 to another mark entirely. Unlike the evolution of Tanjiro's physical abilities - which are routinely explained throughout the series - Tanjiro's mark isn't fully addressed. However, it should gain more clarification and importance in the anime's arcs.

So, how did Tanjiro get his scar? Initially, it's explained as an injury he received as a result of saving his brother from a falling boiling kettle. As such, the fact that his scar changes in episode 4 after being smashed into a tree by the Hand Demon would mean that the mark changes because this incident makes the scar worse - as blood is shown dripping from this spot.

But this doesn't make sense either visually or logically. The burn scar wouldn't be changed into a line of scars by Tanjiro's shattered mask, nor would it change in surface area. It also wouldn't make sense for a scar to become further scarred.

The Manga Goes Deeper Into Demon Slayer's Tanjiro Mark

Demon Slayer Chapter 129

Instead, it's worth considering that Tanjiro's mark was never actually a scar, and instead was always a Demon Slayer Mark - something similar to the marks seen on various demons in the series. These denote significant power in those marked. In the show, Tanjiro's father Tanjuro is shown with the exact same head "scar" as his son - and it seems unlikely that the explanation for this is that they both had the exact same scarring incident with a boiling hot kettle. As such, it's clear this is an inherited trait.

With this in mind, his battle against the Hand Demon makes better sense, as this is the first truly powerful demon Tanjiro fights in Demon Slayer - even if it does pale in comparison to his later opponents. In the manga, far more light is shed on Tanjiro's mark - especially in explaining how the Mark manifests.

Chapter 129 reveals that the Mark appears on those whose bodies go through specific superhuman circumstances - with their heart rate reaching or going over 200 BPM, and their body temperature going to or exceeding 39 degrees Celsius. This would perfectly explain why the incident with the kettle triggered Tanjiro's Mark, as both the temperature of the kettle and the heightened heart rate brought on by concern for his sibling (and pain) would likely result in both of these circumstances being met.

The Deeper Meaning of Tanjiro's Scar Changing in Demon Slayer

Tanjiro's scar changing shape is something of a visual indication of his progress as a demon slayer. The scar changes as he gains more experience in battle, and gradually takes on that flame-like shape that's clearly a Demon Slayer Mark. Even in battle, it will grow larger and more prominent, although this effect somewhat dissipates when the fighting has finished, the way the Marks on Tokito and others disappeared. Moreso than his strength, though, it shows progress at learning more about the past.

The flame-like nature of the marking calls to mind Tanjiro's ability to perform the Hinokami Kagura, a dance derived from the original Sun Breathing style. As it turns out, Tanjiro has a long family connection (though not biologically) to Yoriichi Tsugikuni, the creator of Sun Breathing. It's known that being in the presence of someone with a Demon Slayer Mark can encourage similar marks to appear on others, and it seems that applied to Tanjiro's ancestors who associated with Yoriichi as well. Yoriichi himself was born with a mark, indicating that may be the case for Tanjiro as well.

Why Tanjiro's Scar Didn't Change in Demon Slayer Season 3

Demon Slayer season 3 followed the next storyline from the manga, the Swordsmith Village Arc. In it, Tanjiro works with two Hashira, Mitsuri Kanroji and Muichiro Tokito, as well as Genya Shinazugawa, to protect the village from attacking Upper Six demons. While Tanjiro definitely faced some dangerous opponents, his scar remained more or less the same as it was prior to the Swordsmith Village arc. Instead, fans were given the chance to see Tokito develop a Demon Slayer Mark of his own, thus introducing the question of just what these marks are and setting Tanjiro up to finally receive some information on them in season 4.

Should Demon Slayer season 4 and beyond continue to follow in the footsteps of the plot of the original manga, not only will this be made more apparent, but the Mark will become a far more important aspect of the plot for several reasons. For now though, it's worth noting only that it's more important than just a scar that looks cool - as Demon Slayer's visual appeal and attention to plot details tend to go hand in hand.

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