Battle Trial - Ryuki World

Upon arriving in the World of Ryuki, Natsumi goes to the Atashi Journal headquarters to learn about the world's Kamen Riders from its editor, Reiko Momoi. After Natsumi's arrival at the journal's offices, Reiko is mysteriously murdered, leaving Natsumi as the culprit as she has a small fork in her hand. Natsumi is arrested under suspicion of murder and is to be sentenced with a Kamen Rider Trial: a system where Kamen Riders fight in the Mirror World to determine the outcome of criminal cases.