Rimuru Tempest, a slime who evolved into a demon lord to save his friends. He and his friends established the Jura Tempest Federation, a land of monsters.

In Raja, a small country located to the west, A long-running conspiracy swirls around the mysterious power of the queen.

Then, Hiiro, a "Survivor of the Ogres", suddenly appears in front of Rimuru and his friends. They are reunited with a man who used to be the brother of Benimaru and his friends.

The severed "scarlet bonds" now become the guiding light for a new fight.