In Demon Slayer: Kimetsu no Yaiba Mugen Train Arc, Tanjiro Kamado and his fellow Demon Slayer members embark on a mission aboard the Infinity Train. Their new mission is to investigate a series of mysterious disappearances, carried out by a demon that has been terrorizing passengers and killing the demon slayers who oppose it.
Note: The first episode is entirely anime original. Episodes 2-7 are a re-edited version of the movie featuring new scenes and music.
— Description from AniList community (anilist.co).
