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...
Then you, the true demon, 
would gain even more power.
،ومن ثمّ ستكسب أنت، الشّيطان الحقيقي
قوّة أكبر فأكبر
Damit sie noch stärker werden.
Entonces, el ente demoníaco
conseguiría aún más poder.
Entonces, el ente demoníaco
conseguiría aún más poder.
Tout cela pour devenir
encore plus puissants…
così che questi
Com isso os verdadeiros demônios
conseguem ainda mais poder.
И тогда ты сам
обретёшь ещё большую силу.