This story takes place before Rimuru's reincarnation. Shizu, also known as the Conqueror of Flames, responds to an urgent request calling her to the Kingdom of Filtwood. When she reaches the castle, many adventurers are already there. What request could have demanded such a huge gathering? It turns out a demon has been revived, and the adventurers have been called to subjugate it. It is said that more than ten of the most skilled adventurers have already been killed by this demon. But there is more to this request than meets the eye...
If this demon drove the 
kingdom to the brink of ruin
إذا كان هذا الشّيطان قد دفعَ المملكة
إلى حافّة الدّمار
Wenn euer Land am Rande
der Vernichtung steht
Si casi llevó a este reino a la ruina
Si le faltó poco para arruinar el reino
S’il a pu vaincre
les Ailes des glaciers,
Se è diventato un pericolo per l'intero regno
Se esse demônio levou
o reino à beira da ruína
Этот демон едва не погубил королевство,