Happy to oblige! Some spoilers below.
Setting: 30 years in the past, flame-powered mutants appeared on Earth, leading to a mutant/human conflict that killed half the population. This fact is mentioned in the prologue and then never alluded to again. The action takes place in Promepolis, a shiny new city constructed post-apocalypse and vaguely located somewhere in the western US.
Main cast:
Galo, our protagonist, rookie member of a fire rescue team that uses mechs to do their firefighting/rescuing because it looks really cool, dammit. Very enthusiastic about his job, not dumb enough to be a true himbo IMO.
Lio, our antagonist for the first half hour, dramatically costumed five-foot-nothing leader of a mutant terrorist group, frequently annoyed.
Kray, industrial magnate, governor of Promepolis, and Galo's personal hero since he saved Galo's life when he was a little kid.
The conflict between Galo and Lio lasts until the 30 minute mark, when we find out that Kray is doing experiments toward using the mutants as a fuel source, which inevitably kills them, and really all the mutants want is to be left the hell alone. Also the entire planet will be destroyed in six months. Kray plans to take a few thousand people with him on a dead-mutant-powered spaceship and leave the rest of humanity to die.
Galo and Lio team up to fight Kray (there are more mechs involved, naturally), save the planet, save each other, form one of the world's most adorable ships. That isn't just fan culture at work; the movie is not explicitly gay, but it takes actual effort to read it otherwise.
I'm leaving a lot out here, obviously. The world-building is sketchy, the soundtrack is fantastic, the animation is solid. It's a very fun movie, and if you think about any of it for more than 30 seconds there is horror everywhere. :D I love it.
