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!

After concluding the opening ceremony of the Demon Kingdom Federation Tempest, Rimuru and his companions are invited by the Celestial Emperor Hermesia of the great elven nation – the Magi Dynasty Salion – to visit her private resort island. As the group enjoys their brief vacation, a mysterious woman named Yura appears. A new incident unfolds against the backdrop of the boundless azure sea.