That Time I Got Reincarnated as a Slime the Movie: Scarlet Bond

An old-school magical artifact called the Queen is rumoured to be functioning again in the small kingdom of Raja, west of Tempest. Hiiro — a survivor of the ogre tribe Rimuru's circle absorbed years earlier — has been tracking the artifact since his clan was wiped out. The film opens with Rimuru on a diplomatic visit to Raja and Hiiro arriving at the same court for entirely separate reasons. The investigation that pulls them together is the manga's Queen Of Nightmares arc, condensed into a single feature, and the running argument between Rimuru's diplomatic instincts and Hiiro's plan.