Tanjiro, who's undergoing rehabilitation training at the Butterfly Mansion, works hard to keep up his Total Concentration Breathing techniques all day long. Though at first, he's helpless against Kanao, a swordswoman in his class who's training him, he slowly but surely begins to make some headway. Seeing Tanjiro devote himself to training every single day, Zenitsu and Inosuke resume training as well, but..

Tanjirou and the group have completed their rehabilitation training at the Butterfly Mansion, and they arrive to their next mission on the Mugen Train, where over 40 people have disappeared in a very short period of time.
Tanjirou and Nezuko, along with Zen'itsu and Inosuke, join one of the most powerful swordsmen within the Demon Slayer Corps, Flame Hashira Rengoku Kyoujurou, to face the demon aboard the Mugen Train on track to despair.