Tanjiro, Nezuko, Zenitsu, and Inosuke board a train to assist the Flame Hashira Kyōjurō Rengoku in his mission to hunt for a demon that has killed many demon slayers. Soon after boarding, all of them are enchanted and fall into a deep sleep. Enmu, Lower Rank One of the Twelve Kizuki, instructs four passengers, all suffering from severe insomnia, to enter the demon slayers' dreams and destroy their spiritual cores so that they can't wake up again.