That Time I Got Reincarnated as a Slime: Scarlet Bond is somewhat of a rarity in original tie-in films to TV anime that are adapted from another medium. Most films in this vein are either not in continuity or are so removed from the main story that they might as well be. And while Scarlet Bond is a largely forgettable tale, its connection to the story of the TV anime helps it rise a bit above similar films.
Because so much has happened to Rimuru Tempest and his loyal companions over the past two seasons of That Time I Got Reincarnated as a Slime, it's easy to forget the lingering repercussions of previous events. Scarlet Bond brings this back into focus by spotlighting an outsider's view of Tempest.
Before Geld and the Orcs built roads to connect Tempest to the outside world, they were a scourge that devoured thousands and committed genocide against the Ogres. While Benimaru, Shion, and the others may have forgiven the Orcs and come to see them as valuable, stalwart companions, the rest of the world views the remaining Orcs as having been taken in by an upstart Demon Lord who also resurrected the most dangerous being in existence, Veldora, and led him to kill 20,000 soldiers. (Of course, the truth is quite a bit different than that, but this is what the world at large “knows.”)
As both a survivor of the Ogre genocide and a member of Benimaru's tribe,Scarlet Bond's protagonist Hiiro is thus a character filled with justified rage for the past but has no outlet to unleash it upon. After all, killing your long-lost family's new friends and starting an international incident is hardly an option—even if Geld is willing to die for the sins of his people. But knowing that logically doesn't make the rage magically go away. The anger can be pounded down and suppressed, but that doesn't mean it isn't still there, waiting for a chance to break free. Through Hiiro, the film explores this internal struggle and how people attempt to move on from such deep hurt while also functioning as a compelling introduction to a central character who doesn't enter the main story for another story arc or two.
Yet there's one thing that prevents Scarlet Bond from becoming a genuinely memorable entry in the Reincarnated as a Slime franchise: Rimuru Tempest himself. At this point in the story, Rimuru is so powerful that only a few beings could (and would) stand directly against him. But of course, those people all have vital roles to play in the main story, so they are otherwise indisposed. This means that no enemy in this film poses even the slightest threat to Rimuru. The film's climax, despite its attempts at heartrending drama, only plays out the way it does because Rimuru is just playing with his food, so to speak.
When it comes down to it, the way Rimuru plays cat and mouse with the film's instantly forgettable villain makes him seem like the true antagonist due to the sheer amount of irresponsibility he shows. As vital infrastructure and buildings are being destroyed and Benimaru struggles to contain the damage, Rimuru “tries” and fails to catch the villain—even though he's mounted on Ranga and the villain is on a literal minecart. And as we see in this very film that Ragna can move as fast as a flying dragon, it's hard not to think Rimuru is dragging the chase out for little more than his amusement. With all his power, there is no reason to believe that Rimuru couldn't have captured the villain and dealt with the more physical threat long before things come to a head the way they do in the film's actual drama-filled climax. Or, to put it another way, it feels like Rimuru is so powerful he gets in the way of the story the film wants to tell—and so the creators have dealt with this by writing him to be either incompetent, irresponsible, or just plain evil.
On the visual side of things, Scarlet Bond is a step up from the TV series. There is a ton of dynamic camera movement in the action scenes, and the magic and fire effects throughout are superb. That said, the film does have a bit of an issue with the weapons in the movie—the swords constantly shift in size and look odd at certain angles—but this is just a minor complaint. As for the music, it's largely forgettable, except for the film's ending theme, "Make Me Feel Better," courtesy of singer MindaRyn, which adds another connection between the TV series and the movie.
Overall, That Time I Got Reincarnated as a Slime: Scarlet Bond is above average as far as original, tie-in anime films go. There were apparent attempts to connect the movie in a meaningful way to both the past and future of the story, and the film's newly created lead, Hiiro, is a character worth exploring. But other than that, everything about the film is forgettable, from the villains and the one-off heroine to the plot and setting. And the way that Rimuru is utilized in the film hurts his character overall by making him seem either incompetent or simply uncaring about the suffering of others. Still, if you're a fan of the anime, there's a lot of fun to be had by putting the spotlight back on our evolved Ogres for a while, and if you're a fan of the novels, there's even more to enjoy here.