That Time I Got Reincarnated as a Slime (2018)

S1E24 Black and the Mask

Before Rimuru's reincarnation, Shizu, known as the Conqueror of Flames, receives an urgent summons to the Kingdom of Filtwood. Upon her arrival at the castle, she finds a large assembly of adventurers already gathered. What could warrant such a significant turnout? The answer reveals itself: a demon has been resurrected, and these brave souls have been called to defeat it. The situation is dire, as reports indicate that over ten top-tier adventurers have already fallen victim to this creature. However, there’s a deeper layer to this mission that remains hidden from view...