A retired hero so strong he's bored is the setup, but the real draw is watching someone who has already won everything fight anyway. The hand-to-hand combat animates with a clarity and weight that makes every exchange feel like it matters, even when the story moves too fast to let you breathe. Twelve minutes per episode means the pacing never stops to let the premise settle, but if you're here for fluid fights and a protagonist who treats godlike power like a tired job, it delivers exactly that.

Zero was humanity's first true superhero, and in his wake many more heroes rose up to follow his example. After five years of war, he vanished without leaving any trace. The story is set in a world where justice clashes with evil and where magic and science are woven together, and it centers on how the strongest hero spends his retirement. The series is a 12-episode action fantasy ONA with science fiction elements.