This is a condensed recap that gets away with being a recap because the final twenty minutes exist, new content that recontextualizes everything you already know. The TV series built Simon into a man who lost his way trying to save the world. This movie asks what happens when he has to choose between saving it and saving the person who made him believe it was worth saving in the first place. Most of the runtime is expensive footage recycling, and it feels like it. But that ending carries the weight the series earned, which is all a real fan needs.

Simon is a shy, naive boy who digs tunnels to expand Jeeha, an underground village where people have lived for centuries under constant threat of quakes and cave-ins. Kamina insists a surface world exists above them. When the ceiling collapses and a giant Gunmen falls in, followed by a rifle-wielding girl named Yoko, the three escape upward in Lagann, a strange robot Simon unearthed. The surface turns out to be ruled by the Spiral King and his beastmen, and the group sets out to challenge him. The film re-edits the first part of the TV series with some new animation, mixing mecha action, comedy, drama and romance.