Demon Slayer: Infinity Castle Is Finally Streaming, But There’s A Season You Need To Watch First

Published Sep 29, 2026, 5:50 PM EDT Sky Blanton is a Movie Contributor at ScreenRant with professional experience covering movies, television, and pop culture. Her published work spans news, interviews, features, and opinion pieces, with a focus on film, franchise storytelling, and the entertainment industry. She earned her bachelor's degree in Communications with a concentration in Professional Writing and a minor in Business Writing from Southern New Hampshire University. Before pressing play on Demon Slayer: Infinity Castle on Disney+, there is one part of the anime worth going back to first. Thankfully, that does not mean restarting Demon Slayer: Kimetsu no Yaiba from season 1. If you still remember the major beats of the series, season 4 is the only part you really need to revisit because Infinity Castle begins almost exactly where the Hashira Training Arc leaves off. Season 4 puts the final pieces in place for the fight with Muzan. Tanjiro trains under several Hashira, the Corps discuss the Demon Slayer Marks that appeared during the Swordsmith Village battle, and the Hashira begin strengthening the rest of the Demon Slayer Corps for what is coming. This is crucial, as Tanjiro's sister Nezuko being able to survive sunlight gives her an ability that Muzan has spent centuries trying to achieve himself, pushing him closer to a direct confrontation. The finale then sends the story straight into Muzan's stronghold. Muzan reaches the Ubuyashiki Mansion the Demon Slayer Corps are based in, Tanjiro and the Hashira rush toward the confrontation, and they are plunged into the Infinity Castle. The movie picks up from there instead of resetting the story, which is why season 4 is the one stretch worth revisiting before hitting play. Demon Slayer: The Story So Far By the time Demon Slayer: Kimetsu no Yaiba season 4 starts, Tanjiro is no longer fighting from the bottom of the ladder. He has survived the Mugen Train, helped take down Daki and Gyutaro in the Entertainment District, and made it through the Swordsmith Village battle alongside Muichiro Tokito and Mitsuri Kanroji. Those wins are a huge deal because Muzan’s Upper Ranks had gone generations without being seriously challenged. For the first time in a very long time, the Demon Slayer Corps is actually cutting into the group that has kept everyone terrified of Muzan. The real turning point comes at the end of the Swordsmith Village Arc. Nezuko survives direct sunlight, something demons are not supposed to be able to do, and that immediately makes her far more important to Muzan. He has spent centuries trying to overcome that same weakness, so Nezuko suddenly represents something he has never been able to achieve himself. From that moment on, she is no longer just Tanjiro’s sister or the demon traveling with him. She becomes the one person Muzan has the strongest reason to find. Season 4 picks up with the Corps knowing the situation has changed. Tanjiro is still recovering, while the Hashira gather at the Ubuyashiki Mansion to discuss the marks that appeared during the Swordsmith Village battle and what they could mean. Their answer is to start Hashira Training and push the entire Corps harder before Muzan makes his move. That is the position Infinity Castle inherits. Tanjiro has proven he can survive battles with Upper Rank demons, Nezuko has become Muzan’s priority, and the Hashira are preparing for a fight they know is coming. Season 4 is the point where all of those plot threads stop running separately and start heading toward the same place. Why You Should Watch Season 4's Hashira Training Arc Before Infinity Castle Season 4 finally lets Tanjiro spend meaningful time with the Hashira who take on much bigger roles once Infinity Castle begins. Tanjiro spends real time training under Gyomei, Sanemi, Obanai, and the others, which features useful character moments that benefit the movie when everyone is scattered into separate battles. You already know how these these characters think, how they fight, and where some of the tension between them comes from. The finale finally turns all that preparation into an actual confrontation. Muzan shows up at the Ubuyashiki estate, the Hashira try to stop him, and before they can get their footing, Nakime opens the Infinity Castle beneath them. One second they are charging toward Muzan, and the next they are falling through his fortress with no idea where they will land or who they will face. That is why skipping season 4 leaves such a noticeable gap. Infinity Castle opens after the Demon Slayers have already been scattered through Muzan’s fortress, with the Hashira forced into battles they spent the entire previous arc preparing for. As such, watching the Hashira Training Arc first means those opening minutes feel like the next step in the story instead of something you have to piece together after the fighting has already started. Release Date September 12, 2025 Runtime 156 Minutes Director Haruo Sotozaki, Hikaru Kondo Cast Natsuki Hanae Tanjiro Kamado (voice) Akari Kito Nezuko Kamado (voice) Writers Koyoharu Gotouge, Hikaru Kondo Producers Masanori Miyake, Takao Shimazaki, Tatsuro Hayashi, Yuma Takahashi