Shinichi Kido is the protagonist known as Kamen Rider No. 0 in the Kamen Rider series. As the first test subject of the Shocker organization's Rider System, Shinichi rebels against his creators and becomes a hero fighting for justice. His transformation into Kamen Rider No. 0 marks the origin of the legendary Kamen Riders. Shinichi's journey is marked by his struggle to reclaim his humanity and protect others from suffering the same fate, setting the stage for the Kamen Rider legacy.