Sougo Tokiwa is the main protagonist of the series Kamen Rider Zi-O. As the destined King of Time, he transforms into Kamen Rider Zi-O and later gains the ultimate form called Kamen Rider GrandZi-O. Sougo is a high school student with a kind heart and a dream to become a benevolent king. Throughout the series, he travels through time, meeting various past Kamen Riders and confronting threats that could alter history. Kamen Rider GrandZi-O embodies the power of all past Heisei Riders, making Sougo a pivotal hero in the series.