HS: "The animation style is nicely simplistic. Different portraits are used as establishing shots and then just a few characters or objects move, almost as if they are stuck in a painting. It’s a neat trick that makes for a unique style. The theme songs by Kokia and Ali Project are also catchy, featuring dizzying vocals that are somewhat dreamy.
The series is not for children. There’s a good deal of animated violence and brief animated nudity. Most of the action is centered on death and murder, so Phantom proves to be quite dark. Zwei and Ein are not exactly a happy couple. Sometimes they are forced to pose as boyfriend-girlfriend, but it’s all a ruse. They are, in fact, taking notes on their next assassination attempt. Behind the smiles and doting eyes are cold-blooded killers and blank stares. The whole point of the series is whether that darkness is permanent or escapable."