During their stay in the capital of Milishion, the adventurers of Dead End decide to split up for a day to run their errands. While Rudeus Greyrat has his plans derailed by a troublesome scene, the party's swordswoman, Eris Boreas Greyrat, finds herself with nothing to do. Deciding to embark on an adventure to slay goblins, Eris crosses paths with a cocky but talented mage named Cliff Grimoire. Though Eris refuses his company, Cliff stubbornly ignores her wishes and dares her to explore the perilous forest surrounding the city. Accepting his challenge, Eris ventures into the forest with the mage, where the two encounter something far more repulsive than mere goblins. [Written by MAL Rewrite]

Mushoku Tensei: Isekai Ittara Honki Dasu - Eris no Goblin Toubatsu is an unaired episode bundled with the fourth Mushoku Tensei: Isekai Ittara Honki Dasu Blu-ray volume.