A long-running conspiracy is swirling over a mysterious power wielded by the Queen in Raja, a small country west of Tempest. When a slime who evolved into a Demon Lord named Rimuru Tempest crosses paths with Hiiro, a survivor of the Ogre race, an incredible adventure packed with new characters begins. The power of bonds will be put to the test!

In this spinoff series, Rimuru gets his hands on a notebook and decides to compose a record of his many adventures. But where to begin?

With the earth alliance weakened, Haruo weighs siding with the Exif, whose death cult is summoning a monster that can destroy the world.

On Earth, Haruo and his companions make contact with the indigenous Houtua tribe. To defeat Godzilla, they set out for the old Mechagodzilla facility.