If you loved I Am a Hero, try Gantz: Perfect Answer
A bridge between a film you've already seen and one most people haven't. Here's what they share, and what the second one does that the first one doesn't.
What they share
Both films are directed by Shinsuke Sato, and they sit in Action / Horror territory. If that's the register that drew you to I Am a Hero, the second film will land in a comparable space — through a different lens.
What Gantz: Perfect Answer is
Tokyo. A humid summer night. Splatter of blood. The black sphere demands more lives, but one fighter refuses, another craves the power, and still more aliens arrive. Sato's sequel ratchets up the manga-violence.

