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

By this point in the story, a whole nation of monsters has been built, alliances forged, and threats handled that would flatten most isekai protagonists. So what happens when his commander Benimaru finds out his older brother is still alive? That's the setup for this movie. Hiiro, an ogre survivor everyone thought was dead, shows up in Tempest asking for help. Turns out he's been living in Raja, a small kingdom to the west, where Queen Towa has been sacrificing her own life force to keep her people safe from a cursed magical artifact. Rimuru and crew head out to investigate, and naturally things get more complicated than a simple rescue mission. There's a conspiracy brewing in Raja, and the queen's power is at the center of it. The movie does a solid job expanding the world beyond Tempest — Raja feels like a real place with its own politics and problems, not just a throwaway setting for a film arc. Hiiro and Towa are genuinely interesting additions, and Benimaru gets more emotional depth than the main series usually gives him. The action sequences from Studio 8bit look great on a movie budget, and the comedy beats still land without undercutting the stakes. If you're into isekai with actual world-building like Overlord or Re:Zero, and you're already following Slime, this is a natural continuation. Newcomers might feel a bit lost, though — definitely watch the TV series first.