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 the analog watch-themed 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 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.
Utilizing the Ride Watch in conjunction with the belt, Sougo can transform into Kamen Rider Zi-O. While transformed, he can perform the finisher. He also wields the , which has a for performing the finisher and a for performing the finisher. His personal vehicles are the motorcycle, which is summoned from the Ride Watch, and the mecha, which can switch between its flying and its humanoid . Additionally, he possesses other Ride Watches that allow him to assume forms based on his 19 Heisei Kamen Rider predecessors called , which are as follows: : An auxiliary form accessed from the Ride Watch that grants increased leg strength. In this form, Sougo wields the tekkō, based on Kamen Rider Build's Drill Crusher. His finisher in this form is the . This form first appears in the film Kamen Rider Build the Movie: Be the One. : An auxiliary form accessed from the Ride Watch that grants the ability to generate a digital field with chocolate block-like platforms. In this form, Sougo is equipped with a pair of gauntlets, based on Kamen Rider Ex-Aid's Gashacon Breaker. His finisher in this form is the . : An auxiliary form accessed from the Ride Watch that grants the use of the ability to transform into an aircraft-like state. In this form, Sougo is equipped with a pair of self-propelling gauntlets, based on Kamen Rider Fourze's Rocket Module. His finisher in this form is the . : An auxiliary form accessed from the Ride Watch that grants superhuman jumping and senses. In this form, Sougo is equipped with the right forearm-mounted , based on Kamen Rider OOO's Tora Claws. His finisher in this form is the . : An auxiliary form accessed from the Ride Watch that grants the ability to open portals. In this form, Sougo carries six swords, based on Kamen Rider Gaim's Daidaimaru, to dual wield in three pairs. His finisher in this form is the . Ghost Armor: An auxiliary form accessed from the Ghost Ride Watch that grants similar capabilities as Geiz's version. Sougo's finisher in this form is the . : An upgrade form accessed from the Ride Watch that can be augmented with one of Sougo's predecessors' power-up forms by combining the Decade Ride Watch with their corresponding Ride Watch. In this form, he wields the wristwatch-like , which allows him to perform varying attacks based on the powers of his predecessors. His finishers in this form are the via the Ziku-Driver and the and via the Ride Heisaber. : An enhanced version of Decade Armor accessed from the Decade and Build Ride Watches that augments Sougo with Kamen Rider Build's Rabbit Tank Sparkling Form, which grants the use of the Drill Crusher Crusher to dual wield alongside the Ride Heisaber. : An enhanced version of Decade Armor accessed from the Decade and Ghost Ride Watches that augments Sougo with Kamen Rider Ghost's Grateful Damashii, which grants the combined powers of all 15 heroic Eyecons. : An enhanced version of Decade Armor accessed from the Decade and Ex-Aid Ride Watches that augments Sougo with Kamen Rider Ex-Aid's Double Action Gamer Level XX, which splits him into the azure-colored Decade Armor Ex-Aid Form L and the orange-colored Decade Armor Ex-Aid Form R. : An enhanced version of Decade Armor accessed from the Decade and OOO Ride Watches that augments Sougo with Kamen Rider OOO's Tajadol Combo, which grants flight capabilities. : An enhanced version of Decade Armor accessed from the Decade and Ride Watches that augments Sougo with Kamen Rider Ryuki Survive, which grants the use of the Drag Visor Zwei to dual wield alongside the Ride Heisaber. This form appears exclusively in the web series spin-off Rider Time: Kamen Rider Ryuki. : An enhanced version of Decade Armor accessed from the Decade and Ride Watches that augments Sougo with Kamen Rider Saber, which grants pyrokinesis. This form appears exclusively in the web series spin-off Rider Time: Kamen Rider Zi-O vs. Decade: 7 of Zi-Os!. : An auxiliary form accessed from the Ride Watch that grants aerokinesis and the use of two units, based on Kamen Rider W's Cyclone and Joker Memories, for combat assistance. Sougo's finisher in this form is the . This form first appears in the crossover film Kamen Rider Heisei Generations Forever. : An auxiliary form accessed from the Ride Watch that grants superhuman athleticism. Sougo's finisher in this form is the . This form first appears in the crossover film Kamen Rider Heisei Generations Forever.
Amidst his journey, Sougo acquires unique Ride Watches that allow him to achieve the following power-up forms: : Sougo's super form accessed from the two-in-one that grants the ability to see seconds into the future. While transformed, he wields the sword, which allows him to perform the and attacks. He can also combine the Saikyo Girade and Zikan Girade to form the broadsword. His finishers in this form are the via the Ziku-Driver and the via the Saikyo Zikan Girade. : A fusion form between Kamen Riders Zi-O, Geiz, and Woz accessed from the Ride Watch that allows the trio to use all of their powers and weapons at once. Their finisher in this form is the . : A variant of Kamen Rider Zi-O Trinity that replaces Woz with Tsukuyomi. This form appears exclusively in the tie-in novel Novel: Kamen Rider Zi-O. : Sougo's final form accessed from the Ride Watch that grants chronokinesis and the ability to either summon any of his predecessors from their active timeline to fight by his side or use their weapons along with his own. His finisher in this form is the . : A fusion form between Kamen Riders Zi-O and Ohma Zi-O accessed from the latter's personal Ride Watch that allows the former to use half of his future self's powers. Sougo's finisher in this form is the . This form appears exclusively in the film Kamen Rider Zi-O the Movie: Over Quartzer.
During the final battle, Souga's Ziku-Driver evolves into the Ohma Zi-O Driver, allowing him to transform into Kamen Rider Ohma Zi-O. While transformed, he gains the power to destroy enemies with a single attack. His finisher is the .
Sougo Tokiwa is portrayed by while and portray him as a child and younger child, respectively.
Mirror Sougo Tokiwa The is a cynical and power-hungry version of the original Sougo from the Mirror World. Meeting his real world counterpart during the events of Another Ryuga's reign of terror, Mirror Sougo torments his counterpart over his perceived futile attempt at defying his fate as Ohma Zi-O. When Sougo reaffirms his belief and acknowledges his darker self, the Mirror Sougo concedes and gives the former half of the Zi-O Ride Watch II. Like his real life counterpart, the Mirror Sougo can also transform into Zi-O, with his suit being a mirrored copy of the original.
In the tie-in novel Novel: Kamen Rider Zi-O, another version of Mirror Sougo is brought into existence when the Third Woz interferes with the timeline. This Mirror Sougo fuses with his real world counterpart to become and collect most of the Another Watches to become Another Ohma Zi-O. He later joins forces with Third Woz to obtain the Decade Ride Watch and manipulate the original timeline so that Sougo never meets Geiz and Tsukuyomi and ensure he becomes Ohma Zi-O. After absorbing Geiz and Tsukuyomi's Another Watches to become Another Ohma Zi-O Trinity, Inner Sougo is defeated Zi-O Trinity Version Geiz & Tsukuyomi.
Mirror Sougo Tokiwa is portrayed by So Okuno, who also portrays the real world version of Sougo Tokiwa.
Alternate Sougo Tokiwa In the Rider Time web series Decade VS Zi-O and Zi-O VS Decade, several alternate timeline iterations of Sougo Tokiwa are introduced as supporting characters, each of whom retain the ability to transform into Zi-O. Excluding the android Sougo, the rest of the alternate Sougos are addressed alphabetically, with the "prime" Sougo designated as "A". Most of the alternative versions are hunted down and killed by Tsukasa in order to prevent the merging of alternate universes caused by the True Sougo.