According to director Goichi Suda, Romeo's design was based on the main character of a cancelled project called "Zombie Rider", whose main character would have been a human-zombie hybrid. The project never came to fruition, but Suda decided to use the design for Romeo, who is similarly half-dead. These ideas were tweaked in the process, such as updating his backstory so that his grandfather Ben used the Dead Gear to bring him back to life.