Aoki Hagane no Arpeggio, known as Arpeggio of Blue Steel, is a Japanese anime and manga series that combines science fiction and naval warfare. The story is set in a future where mysterious sentient warships known as the Fleet of Fog have taken control of the world's oceans. Humanity's only hope lies with a group of young cadets who command a rogue Fog submarine. The series explores themes of artificial intelligence, loyalty, and human survival.