Warning: Contains spoilers for Demon Slayer: Kimetsu no Yaiba season 2.
Season two of Demon Slayer: Kimetsu no Yaiba has just dropped a major reveal about Tanjiro Kamado in its latest episode. After spending nearly two months recapping the Mugen Train movie, season two of the anime has started moving the story forward with its “Entertainment District” arc. In tandem with that, the anime has taken steps to set up the level of importance Tanjiro and his family will have in the story in a major way.
In Demon Slayer: Kimetsu no Yaiba, the titular Demon Slayers fight against demons using the Breathing Styles technique, which utilizes hyper-focused breathing to grant the user enhanced strength and reflexes to give them the power to kill demons with their specialized swords. Tanjiro was trained in the Water Breathing Style, but during his fight with the Lower Moon Demon Rui near the end of the first season, he suddenly uses a new, more powerful Breathing Style called the Hinokami Kagura, which was actually a dance his father, Tanjuro Kamado, taught him before his death as a dance. The first season ends with Tanjiro wanting to learn the truth, and part of the "Mugen Train" arc's ending has the Flame Pillar Rengoku telling Tanjiro that there might be information about the Hinokami Kagura somewhere at his family’s home.
That plot point finally gets paid off in season two with the reveal of Tanjiro’s Breathing Style being the most important one in the story. In Demon Slayer season 2 episode 8 - the first episode of the “Entertainment District” arc - Tanjiro learns from Rengoku’s father that the Hinokami Kagura’s true form is Sun Breathing, the original Breathing Style that all others are derived from and the strongest one of them all. It was already clear that the Hinokami Kagura was a powerful technique, but it’s now been fully established as far above its contemporaries.
With the true nature of the Hinokami Kagura also comes an idea of the importance Demon Slayer's Tanjiro is due to have in the fight against Muzan. As the protagonist, Tanjiro fighting the main villain of the series at the end of it all should be a given, as there are few other ways a story would end. However, with the Hinokami Kagura being established as the strongest Breathing Style, it’s likely that the situation will evolve to him being the only one capable of defeating him, or at least someone who will definitively need to contribute to the final fight.
The reveal also adds more to the theory of the connection between Muzan and Tanjiro’s father, Tanjuro. Demon Slayer's Muzan wants to kill Tanjiro because he wears the same earrings as a Demon Slayer who nearly killed him in the past, and anime viewers have long theorized that Tanjuro was that Demon Slayer on account of how they have similar hairstyles and how Tanjiro was able to weaponize the Hinokami Kagura. With the reveal that the Hinokami Kagura is actually Sun Breathing, the theory is all the more plausible for those focusing on solely the anime.
The manga, having ended nearly two years ago, does end up giving a more definitive statement of the Kamado family’s connection to Muzan and Sun Breathing - but for anyone only watching the Demon Slayer anime, it’s still something to think about. Either way, Tanjiro mastering the Breathing Style heavily implied to have been used to nearly kill Muzan would be an ideal course for the story to run. If the story continued on that path, then it would end up as a truly poetic means of bringing the story of Demon Slayer: Kimetsu no Yaiba full circle.