Leviathan

In an alternate 1914, one side of the Great War fights with giant mechanical walkers and the other breeds living airships out of genetically engineered whale DNA. That's the world of Leviathan, and it's as wild as it sounds. Alek is a Habsburg prince on the run after his parents are assassinated, piloting a clunky Stormwalker across enemy territory. Deryn Sharp is a Scottish girl passing herself off as a boy named Dylan so she can crew aboard the HMS Leviathan — a colossal bioengineered warship that literally breathes. When Alek crash-lands into Deryn's world, two people from opposite sides of the conflict have to figure out how to trust each other while hiding who they really are. The character dynamics carry this one hard. Both leads are keeping secrets that could get them killed, and the tension between their loyalties and growing friendship gives the adventure real weight. Orange studio brings its CG expertise to a steampunk-biopunk mashup that looks unlike anything else airing right now, and Joe Hisaishi on the soundtrack doesn't hurt either. If you liked the airship battles and worldbuilding of Last Exile, or the way The Vision of Escaflowne mixed mecha action with personal stakes, this scratches a similar itch. Steamboy fans will also feel right at home with the alt-history tech aesthetic. Twelve episodes, tight pacing, and a setting that rewards curiosity — worth your time.