Mitsuru is a young boy who lives in the 2011 world that has been taken over by the evil organization Shocker following a time paradox. In this altered reality, Shocker rules Japan and humanity is nearly extinct; Mitsuru and his friends Naoki and Shigeru survive by hiding in the ruins and resorting to pickpocketing to get by. He is first encountered when he and Naoki steal a set of O Medals from Eiji Hino and Ankh, inadvertently drawing them into the children’s struggle against Shocker’s forces. Mitsuru is resourceful, street‑smart, and shows a strong will to resist the oppression, though he initially relies on theft for survival. When the DenLiner crew learns that the timeline must be corrected, Mitsuru stows away with Naoki and Ankh on the time‑traveling train to 1971. In the past, he becomes separated from his friend when Naoki is forced to stay behind while Mitsuru returns to the altered present. He later receives a time capsule from Naoki containing a heartfelt message about hope and the true nature of Kamen Riders as heroes of justice. This letter inspires Mitsuru to take action and help rescue the captured Riders, including Eiji Hino and Kotaro Nogami, from Shocker’s public execution. Over the course of the story, he grows from a fearful child into a courageous ally who actively works to restore the rightful timeline. In the film’s conclusion, it is revealed that the adult Naoki, who remained in the past and became a Shocker scientist, is actually Mitsuru’s father, having married the Kamen Rider Scout Nokko. This discovery gives Mitsuru a family and a renewed sense of belonging. While he possesses no superhuman abilities, Mitsuru’s bravery, loyalty to his friends, and determination to oppose Shocker make him an important supporting character who represents the future that the Riders are fighting to protect.