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."

 HiddenLeaf is the best site to watch Mushoku Tensei: Isekai Ittara Honki Dasu Special SUB and DUB in HD quality.