Tanjiro and the group have completed their rehabilitation training at the Butterfly Mansion, and they arrive at their next mission on the Mugen Train, where over forty people have disappeared in a very short span of time. Tanjiro and Nezuko, along with Zenitsu and Inosuke, join one of the most powerful swordsmen of the Demon Slayer Corps, Flame Hashira Kyojuro Rengoku, to face the demon aboard the Mugen Train.