Upon arriving in the World of Ryuki, Natsumi gone 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 was mysteriously murdered, leaving Natsumi as the culprit as she had a small fork in her hand. Natsumi was arrested under suspicion of murder, and was to be sentenced with a Kamen Rider Trial: a system where Kamen Riders fought in the Mirror World to determine the outcome of criminal cases. Natsumi called upon Tsukasa to be her lawyer, who met with Shinji Tatsumi to hear what he knew of what happened to Reiko. As Shinji revealed that he is Kamen Rider Ryuki and he believed Natsumi was framed, his former friend Ren Haguro (Kamen Rider Knight) was fighting in the Kamen Rider Trial, de