Reiko Momoi is a key supporting character in the tokusatsu series Kamen Rider Ryuki. She is a determined and intelligent journalist for the ORE Journal, constantly investigating the mysterious disappearances linked to the Mirror World. In the alternate universe depicted in the film 'Kamen Rider Ryuki: Episode Final,' Reiko becomes Kamen Rider Siren, showcasing her bravery and resolve. As Kamen Rider Siren, she fights alongside other Riders, playing a critical role in the unfolding narrative and the battle against evil.