Demon Slayer's Anime Just Explained a Huge Mystery the Manga Never Did

Nezuko's immunity to sunlight was never explained in Demon Slayer's manga, which is why it's surprising that the anime is fixing that.

Summary

• Nezuko's immunity to sunlight in Demon Slayer could be explained by her consumption of the Blue Spider Lily, as shown in the anime's season 3 finale.
• The Blue Spider Lily bloomed near the Kamado family's home, suggesting that Nezuko had the opportunity to see and eat it, resulting in her immunity to sunlight.
• The explanation behind Nezuko's immunity to sunlight adds depth to the series and highlights the irony of Muzan's failure, as he spent centuries searching for the Blue Spider Lily that only humans could possess.

Warning: spoilers for Demon Slayer: Kimetsu no Yaiba season 3 episode #11 and volume #23.Demon Slayer: Kimetsu no Yaiba season 3 has ended, and it might have finally explained one of the manga’s biggest mysteries, as the “Swordsmith Village” arc ends by revealing Nezuko can’t be killed by sunlight. This makes her unique to other demons, but the manga never actually explained why Nezuko was immune to sunlight, not even in any databooks, making it one of the biggest unresolved mysteries by the end of the series.

The Demon Slayer: Kimetsu no Yaiba manga never explained Nezuko’s immunity to sunlight, but the anime might have finally answered it by showing Tamayo's analysis of her blood in Demon Slayer's season 3 finale.

It’s shown that Nezuko’s blood has blue elements to it, and since the Blue Spider Lily has the power to cure Muzan of his weakness to sunlight, the anime could be revealing that Nezuko’s immunity comes from the Blue Spider Lily at some point. A justification for this can be found in one of the databooks, and it would both explain one of the final twists of the series and make Muzan’s failure even more ironic.

Nezuko's Sunlight Immunity in Demon Slayer is Tied to the Blue Spider Lily

Nezuko having eaten the Blue Spider Lily at some point could explain her immunity to sunlight, and Demon Slayer: Kimetsu no Yaiba has already worked to justify exactly that. According to the second official databook, the Blue Spider Lily bloomed near the Kamado family’s home, with Tanjiro being shown its location by his mother. The same databook also says that Tanjiro was the only child to ever see them bloom, but that doesn’t mean his siblings never saw them Which means Nezuko could have seen and eaten the Blue Spider Lily at some point, which would eventually result in her becoming immune to sunlight as a demon.

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This theory could also explain one of the final twists of the Demon Slayer: Kimetsu no Yaiba manga. Moments before his death, Muzan turned Tanjiro into a demon in a desperate attempt to keep his legacy alive. Just like Nezuko, Tanjiro was immune to sunlight with little explanation other than him being Nezuko’s brother. But assuming Nezuko’s immunity came from eating the Blue Spider Lily, Tanjiro’s immunity could have the same explanation, adding logic to what was otherwise a pair of poorly explained plot twists.

Demon Slayer’s Blue Spider Lily Makes Muzan’s Failure Even Better

The Kamado family knowing where the Blue Spider Lily bloomed can explain how Nezuko was able to become immune to sunlight, and it also works to add even more depth to Muzan’s failure. In the final chapter of Demon Slayer: Kimetsu no Yaiba, it’s revealed that the Blue Spider Lily only blooms a few times a year during the day, meaning that Muzan spent centuries looking for something physically impossible for him to obtain. The irony of that is very apparent, and it becomes even stronger if Tanjiro and Nezuko truly gained the power Muzan sought thanks to the humanity Muzan despised.

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That irony highlights Muzan’s biggest flaw in the series: his utter contempt for humanity. Muzan was never able to understand the value of humanity, and unlike other demons, he took his hatred to the grave as his final gambit fell apart right in front of him. So if Tanjiro and Nezuko managed to survive partly due to the Blue Spider Lily, which they only had because of their humanity, that point manages to be sold even further.

It all adds depth to Demon Slayer: Kimetsu no Yaiba, and the anime going even further to explain Nezuko’s powers is a nagging mystery, well-solved.