According to the recent leaks, Demon Slayer Season 2 will be released in two cour where the first cour will consist of 12 episodes and will cover the Mugen train arc. According to many fans, this might be an indication that the first cour will cover the part which was left uncovered in Demon Slayer-Kimetsu no Yaiba-The Movie: Mugen Train.
Apart from the leaks, officially there is no indication that the Mugen train arc will be covered in the second season. Both the first and second teasers of the Demon Slayer Season 2 indicate the adaptation of Red-light district arcs. The arc involves our protagonists traveling to Yoshiwara, a famed Red-light district, in order to track down a demon. The Hashira Tengen Uzui, who has special abilities around sounds, will be helping our protagonists. While according to the teasers a mysterious female demon will play the villain.
A previous leak has also revealed the Demon Slayer Season 2 will air on Fuji Tv, even though the first season was aired on TOKYO MX (via AnimeHunch). After the success of the Mugen train movie, Fuji Tv aired the first season as a “special show” which resulted in a better rating for the station.
Fans are already excited about the second season and it has since become the most anticipated anime of 2021. The upcoming anime is being realized by studio Ufotable, with its gorgeous and fluid animations. There are a lot of speculations being made about the show and with time things should become more clear as production reveals more information.