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

Summary

• Nezuko’s immunity to sunlight in Demon Slayer may come from eating the Blue Spider Lily, as shown in the anime’s finale.
• The Blue Spider Lily’s significance adds depth to Muzan’s failure, highlighting his contempt for humanity in the series.
• Nezuko’s newfound importance as a key piece in the battle between Slayers and demons sets the stage for a brutal final confrontation.

Warning: spoilers for Demon Slayer: Kimetsu no Yaiba season 3 episode #11 and volume #23.Demon Slayer: Kimetsu no Yaiba season 3 might have ended by explaining 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 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 hinting that Nezuko’s immunity comes from the Blue Spider Lily. A justification for this can be found in one of the Demon Slayer 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 could explain her immunity to sunlight, and Demon Slayer: Kimetsu no Yaiba has already justified it. 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. It’s possible that Nezuko could have seen and eaten the Blue Spider Lily, which would eventually result in her becoming immune to sunlight as a demon.

This theory could also explain one of the final twists of the Demon Slayer: Kimetsu no Yaiba manga. Moments before his death, Muzan turns Tanjiro into a demon to try and 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.

What Nezuko’s Sunlight Immunity Means for the Next Seasons of Demon Slayer

With Nezuko’s immunity to the sun now an open secret known to Muzan, it puts a target on Nezuko’s back, even more so than there was previously. Protecting Nezuko from Muzan and his minions will become a key task to ensure the ultimate victory of the Demon Slayers, as Muzan may be able to replicate Nezuko’s feat if he’s able to get a hold of her, and either experiment upon her or even absorb her into himself like he’s done with certain other demons.

Nezuko has gone from a mere anomaly to one of the key pieces on the chessboard between the Slayers and the demons, too valuable to allow to fall into the wrong hands. That means that going to any lengths to protect her may be called for, even if that means many of the human Demon Slayers have to die to protect her. Given she holds what Muzan has sought for so long, he’s also going to be willing to go to extremes to obtain her, meaning the final battle is just around the corner.

Demon Slayer’s final battle is sure to be an ugly and brutal affair, as many of the strongest demons are still out there and still loyal to Muzan. Given the price that’s been paid to defeat some of the previous Upper Rank demons, there’s likely to be a great amount of death involved on both sides of the conflict. The Hashira Training arc, subject of the fourth season, will be based around preparing for this confrontation.

What Other Mysteries Should Demon Slayer’s Anime Address?

Demon Slayer is fairly tight with its mysteries, as most have been explained in the manga series proper. One of the biggest remaining is how Nezuko was able to retain some semblance of her humanity after becoming a demon, and resist attacking humans, something that even Lady Tamayo wasn’t able to do. It’s possible that the answer to this is the same as the answer to her sunlight immunity: exposure to the Blue Spider Lily. Still, this could stand to be confirmed within the series.

There are a few other questions that the anime could take the time to answer which the manga didn’t. The nature of the Demon Slayer Marks, seen in season 3 of the anime, for example—what relationship do these marks have to demons? Did they exist prior to the existence of demons, and were simply incredibly hard to attain? Unfortunately, the characters only have some distorted rumors from the past and Muichiro’s report on the conditions needed to activate the mark, but a full explanation could potentially be provided by someone like Muzan or Lady Tamayo.

Something else that might be worth exploring is Genya Shinazugawa’s consumption of demon flesh to gain demonic powers. How did Genya first learn of this ability? Did anyone practice it before him? It seems like it would be extremely advantageous to Demon Slayers to do this, but the manga also seems to indicate this power comes at a cost. Was there someone before Genya who did this, whose fate proved it to be a mistake?

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 immune to sunlight, and it also adds 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 becomes even stronger if Tanjiro and Nezuko gained the power Muzan sought thanks to the humanity Muzan despised.

That irony highlights Muzan’s biggest flaw: 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 in front of him. So if Tanjiro and Nezuko survived 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.