Unaired episode included in the fourth Blu-ray volume. The episode will take place during the same time in episode 16 (episode 5 in second cours) and depict what Eris and Ruijerd were up to outside the main story, as teased by the comment "Goblin Extermination."

Kohachi Inugami, a detective who specializes in the occult, arrives at a remote village in the Japanese countryside, tasked by a hostess at a local inn to investigate a string of incidents involving rotting and mutilated livestock corpses that have been appearing for seemingly no reason. While surveying, Inugami notices a peculiar young boy working in the fields. Evaded by his peers and called "Dorotabou" for his stench, the young farmhand is surprised that anybody would take an interest in him. Inugami, piqued with curiosity, enlists Dorotabou in helping him with the investigation, despite scorned looks from the villagers. Unbeknownst to Dorotabou, this investigation will reveal a strange new world to him—one of the beast-like entities known as Kemono existing in tandem with humans—along with breathing new purpose into his previously empty life. [Written by MAL Rewrite]

Futaro has led five quintuplets to the point where they can graduate and pursue their own dreams. Now, finally, they had reached their final school festival. Having decided to make this occasion one to remember, Futaro searches for his feelings for the five quintuplets.

A plague-like wind blows across the arid, sandy expanse of a post-apocalyptic Japan. As it sweeps over the living and nonliving alike, rust is all that remains in its wake. The cause of the catastrophic state of the world is believed to be mushroom spores. Bisco Akaboshi, known as the "Man-Eating Mushroom," is a wanted criminal archer whose arrows instantly grow mushrooms wherever they land. However, he is in truth a "Mushroom Protector," a person who spreads fungi in order to enrich the land and return it to its previous state. Alongside the crab Akutagawa and young doctor Milo Nekoyanagi, Bisco ventures through the wastelands of Japan searching for the legendary "Sabikui"—a panacean mushroom said to devour all forms of rust.