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 fight with possessed swordfighters, they slowly begin to realize the entire mountain is being controlled by a family of Demon spider creatures. A recap film of Kimetsu no Yaiba, covering episodes 15-21 with some new footage and special ending credits.