Anime movies are a great way to keep fans enthralled in the storyline, and that rings true for Demon Slayer. After the first season premiered, we found out that the series' first movie was coming our way and we got Mugen Train. In this film, we follow Tanjiro and Nezuko Kamado, Zenitsu Agatsuma, and Inosuke Hashibira as they join the Hashira Kyōjurō Rengoku on a mission against a powerful demon.In Mugen Train, Rengoku and the gang are up against a lower-rank demon of the Twelve Kizuki named Enmu. But what's interesting about this is that the movie was also made into its own arc in the series. Although they both have the same general details, there are a few key ones that help them stand apart from one another. So, what are those differences and which one should you watch?What are the differences between the 'Mugen Train' arc and the movie?In general, the true difference between the Mugen Train arc and the movie is the amount of detail. The film is just under two hours long, but the arc is divided into seven episodes that are each around 20 minutes long. This means there's way more content in the arc and it gives more context to the characters that you don't get from the movie.For one, the first episode of the arc isn't seen at all in the movie. It acts as a prequel to the movie's content where we see Rengoku eating in a restaurant as he learns about the Mugen Train incidents. And the whole time he's eating, he talks about how tasty the food is, which is a theme we see throughout the movie and the arc.Another difference is that the arc gives us more background into Rengoku that we don't see at all in the movie. \n\nEpisode 2 of the arc features a side plot about a grandmother and her granddaughter that ultimately gives insight into Rengoku and his family. We meet his younger brother and father.Plus, with the arc, we get to see more of the fight between Rengoku and the upper-rank demon Akaza. The arc features a whole episode that's just about this battle. We don't see that much detail in the movie. \n\nAt the end of the day, one isn't necessarily better than the other. The movie is good because it gets you right to the point. If you're rushing to get to Season 2 of Demon Slayer but don't want to sit through hours of content, this is the right choice for you.On the other hand, some may look at that and feel like it's all just filler that gets in the way of the real story. if you're into getting to know Rengoku and his family more, see where his values lie, and fall in love with him for more than his cool flame hair, watch the arc.\n\nYou can watch all of Demon Slayer on Crunchyroll and Hulu.