Kamen Rider Den-O is a Japanese tokusatsu series that is part of the long-running Kamen Rider franchise. It first aired in 2007 and follows the story of a young man named Ryotaro Nogami, who becomes the titular rider. He is able to transform into Den-O with the help of a time-traveling train called the DenLiner and various Imagin, which are creatures that can manipulate time. The series is known for its unique blend of action, comedy, and drama. Each episode features Ryotaro teaming up with different Imagin to battle evil forces while also dealing with his own personal challenges. The show has gained a dedicated fanbase and has spawned several movies and spin-offs, further expanding the Kamen Rider universe.