Following his victory over Clayman, Rimuru ascends as a Demon Lord in the third season of Tensei Shitara Slime Datta Ken. With his dominion now encompassing the vast Great Forest of Jura, Rimuru prepares for a grand celebration to welcome representatives from various races and introduce himself as Demon Lord Rimuru to the world. However, a fabricated declaration of war reaches Holy Knight Captain Hinata in the monster-hating Holy Empire of Lubelius, leading her towards Tempest. In the midst of this misunderstanding, Rimuru faces the daunting task of discerning allies from adversaries as he envisions a harmonious nation where humans and monsters thrive together.