The Diablo vs Violet fight alone justifies the runtime, a choreographed collision between two overpowered beings that actually makes you care who wins. The movie knows it's working with familiar setup, a conspiracy-plot in a minor kingdom that could be background noise in any fantasy show, but it burns through that setup to get to what matters: two survivors of dying races finding each other. Violet becomes canon here, and the animation team spent their actual budget on the moments that proved she belonged.

Raja, a small country lying west of Tempest, is the center of a conspiracy that has been building for a long time around a mysterious power known as "Queen." Rimuru Tempest, a slime who evolved into a Demon Lord, becomes caught up in it alongside his companions. Along the way, Rimuru and his commander Benimaru meet Hiiro, another survivor of the Ogre race who was once Benimaru's brother. The film introduces a range of new characters and puts the strength of bonds to the test. Adapted from the light novels by Fuse with illustrations by Mitz Vah, it is a fantasy adventure that mixes action with comedy.