This episode tells the story of the protagonist Subaru Natsuki, who thought he could live a peaceful life after defeating Petichius Romanee-Contemporary, the Archbishop of Sins of the Witch Cult, but unexpectedly two new Archbishops of Sin appeared! The new Sin Archbishop's superpower caused Rem to fall into a coma and be forgotten by everyone except Subaru. Subaru, Emilia, and Trader Otto took Rem back to Roswaal Mansion, and were greeted by Frederica, the maid who appeared for the first time. The villagers of Alam Village who had gone to the "Sacred Realm" for refuge did not return to the village as planned, so Subaru and his group set out to the "Sacred Realm" to find out. Before setting off, Frederica warned Subaru that he must be wary of Garfiel, a resident of the "Sanctuary", and handed Subaru a mysterious blue gem. However, Subaru didn't know at this time that this gem would actually bring him to the "Desire Witch" Echidna who died 400 years ago!
