After completing recovery training at the Butterfly Mansion, Tanjiro and his friends set out to take on a new mission. On the Infinity Train, something is wrong: at the same time, more than 40 people disappear there! That means Tanjiro, Nezuko, Inosuke, and Zenitsu must face a powerful demon. Having joined forces with one of the strongest swordsmen, the Flame Hashira Kyojuro Rengoku, the heroes challenge the enemy, while the Infinity Train speeds toward the valley of despair.