In a world where humans and demons coexist and compete, people who practice magic and kill demons as their own mission are called demon masters. Qi Xiaoxuan, the captain of the national demon master, met the prodigal Huzi by accident, and the two embarked on a journey to slay demons and protect the Tao together. Now, the world has experienced five hundred years of peace, and the demons are already ready to move, casting a haze on their future...

Eustachius no Shitamachi Sennyuu Dai Sakusen (Eustachius' Incognito Operation Downtown) To get more information about Myne and her strange background, Head Priest Ferdinand sends two nobles, Eustachius and Eckhard, to investigate everything regarding her life within her hometown. However, things do not go the way they expected. Corinna-sama no Otaku Houmon (Visiting Missus Corinna) Otto's wife, Corinna, takes an interest in the outfit that Myne wore at her baptism. Corinna summons her alongside her mother, Eva, and sister, Turi, wishing to know the procedure in making such sophisticated attire and accessories. Naturally, for Myne, she sees an excellent opportunity for profit.

The ancient kingdom of Parros has been invaded by the armies of Mongaul, and its king and queen have been slain. But the "twin pearls of Parros," the princess Rinda and the prince Remus, escape using a strange device hidden in the palace. Lost in Roodwood, they are rescued from Mongaul soldiers by a strange leopard-headed man, who has no memories except for the words "Aurra" and "Guin," which he believes to be his name.