is a Japanese tokusatsu series that serves as the 29th installment in the Kamen Rider franchise and the 20th and final entry in the Heisei era. It follows the exploits of Sougo Tokiwa, a young man who, according to visitors from the future, is destined to become the king who will enslave the entire world, and embarks in a quest to change his fate, meeting several other Kamen Riders from the Heisei era along the way.
Main characters
Sougo Tokiwa
is an 18-year old student, later 19-year old graduate, of who dreamed of becoming a king after experiencing a series of nightmares in his childhood and being visited by a mysterious figure who entrusted him with the prophecy. After surviving a bus accident when he was nine, Sougo became orphaned and since then lived with his great-uncle at 9-to-5. After meeting Tsukuyomi and Geiz, Sougo learns he will become Ohma Zi-O, a tyrant destined to rule the world with an iron fist. Despite being troubled by this possibility, Sougo chooses to continue following his dream while changing his fate, accepting the power to become Kamen Rider Zi-O and declaring that he will become a benevolent tyrant instead. Despite Geiz and Tsukuyomi's reservations, Sougo considers them friends and trusts them with his life, asking both of them to kill him should he follow the path to becoming Ohma Zi-O. All the while, Sougo's predecessor Tsukasa Kadoya secretly watches over him to ensure he succeeds in changing his fate.
Originally a visionary high school student prior to his graduation, Sougo develops other strengths along his journey. Due to his observant nature and keen understanding of human behavior, he became a skilled manipulator capable of outsmarting a genius of Kuroto Dan's caliber. In 2019, Sougo develops the ability to subconsciously create alternate futures, which he initially assumed were prophetic dreams of Kamen Riders from White Woz's timeline. Ever since the bus accident, he also gained chronokinesis like the Time Jackers. However, their leader Swartz erased Sougo's memory of it before the latter regains his powers after he becomes Grand Zi-O.
As Swartz commences a convergence of the A.R. Worlds, Tsukuyomi seemingly betrays Sougo and Geiz is killed saving him. In response, an enraged Sougo becomes Kamen Rider Ohma Zi-O to defeat Swartz himself before sacrificing his newfound power to reset the timeline, negating his destiny and undoing Swartz's damage. Due to this, he relives his senior year in 2018 with altered versions of Geiz, Tsukuyomi, and the Time Jackers as his classmates in the new timeline.
In the sequel special Kamen Rider Zi-O Next Time: Geiz, Majesty, Sougo regains his Rider powers while helping Geiz in his fight against a new White Woz, who became Another Diend to become a savior.
In an alternate timeline depicted in the film Kamen Rider Zi-O the Movie: Over Quartzer, Sougo and his friends help Go Shijima preserve Kamen Rider Drive's history after Oda Nobunaga lost the Battle of Nagashino. Despite succeeding, Black Woz betrays him, taking all of Sougo's Ride Watches and imprisoning him on behalf of the Quartzers. Despite this, Sougo is released by Tsukuyomi and Go and receives the Ohma Zi-O Ride Watch to defeat the Quartzers' leader, an adult version of himself from an alternate timeline. After Sougo defeats his evil counterpart, he is recognized as a king.
In the web-exclusive spin-offs, Rider Time: Kamen Rider Decade vs. Zi-O: The Decade House Death Game and Rider Time: Kamen Rider Zi-O vs. Decade: 7 of Zi-Os!, an alternate universe version of Sougo who became a basketball player becomes trapped in the titular House Death Game and encounters Tsukasa, who was trying to lure the "prime" version of Sougo to the game. The alternative Sougo gives Tsukasa the Saber Ride Watch and asks him to give it to the "prime" Sougo, who is later forced to fight various alternate universe versions of himself.
Sougo uses the belt in conjunction with the to transform into Kamen Rider Zi-O. While transformed, he can perform the finisher and wields the , which has a for performing the finisher and a for performing the finisher. He also owns a , a time traveling vehicle given to him by Tsukuyomi that can switch between and its exo-suit-like , and Woz's Faiz Phone X to communicate with Tsukuyomi and Geiz through time. Additionally, he possesses other Ride Watches that allow him to access forms based on his Heisei Kamen Rider predecessors, which are as follows: