Titular protagonist of [[kamen_rider_zi-o_(series)|Kamen Rider Zi-O]], twenty-ninth show of the Kamen Rider series and twentieth of the Heisei generation, as well as the last, with the abdication of Emperor Akihito at the end of April 2019.

Tokiwa Sougo is an eighteen-year-old high-school student prophesied to become a ruthless tyrant by a girl who claims to have come from fifty years in the future. Determined to defy his fate, he takes up the girl's offer to be trained to become a hero instead, becoming Kamen Rider Zi-O to protect the time-space continuum while encountering other Riders from the Heisei era, another Rider from the future determined to kill him before he becomes the prophesied tyrant, and a mysterious organization tampering with the timeline with Another Riders, monsters based on twisted forms of the Heisei Riders.

As Zi-O, Sougo uses Ridewatches to transform into modified forms of past Heisei-era Riders.