Tanjiro, now a registered Demon Slayer, teams up with fellow slayers Zenitsu and Inosuke to investigate missing person cases on the mountain Natagumo. After the group is split up during a battle with possessed swordfighters, they slowly begin to realize the entire mountain is being controlled by a clan of Demon spider creatures. A recap of Kimetsu no Yaiba episodes 15–21, with new footage and special end credits.