Sougo Tokiwa (Avengers x Kamen Rider Zi-O)

Sougo Tokiwa (常磐ソウゴ) is an 18-year-old (19 as of Episode 34) high school student (graduated as of Episode 29) who joins the Avengers and aids them on their mission to save the world.

Skills

 * Vast Historical Knowledge: According to Tsukuyomi, Sougo excels in history, although Sougo can stumble on remembering some historical figures as Mondo Douan has shown to be more adept in this field than him.
 * Keen Manipulator:  Sougo has a talent for understanding how people would behave and subsequently exploiting people around him to do his bidding like how he tricked both Geiz and Tsukuyomi into watching Another Wizard's magic show with him and how he took advantage of Woz to make him cooperate with him and Geiz. Geiz considered his manipulative capabilities to be a serious threat and an indicator of his potential to become an evil demon king.
 * Timeline Protection/Manipulation: Upon acquiring the Zi-O II Ridewatch, Sougo became immune to any changes in the timeline and gained several abilities allowing to manipulate time as he wishes. These abilities can be performed in and out of Rider form, which implies that the Ridewatch's abilities were bestowed upon him directly. Tsukuyomi openly admitted to Geiz that Oma Zi-O has these abilities as well, which were what made him so fearsome. This caused Tsukuyomi to be paranoid of Sougo, resulting in her avoiding him.
 * Timeline Reversal: Sougo can reverse time, allowing him to redo a certain event and change the future. So far, he has performed this ability twice to reverse the deaths of two people. His first recorded usage of the ability was to undo Geiz' death from Another Ryuga, and the second time was to undo Tsukuyomi's death by Another Kikai. While Sougo has been shown to have only reversed events once, it's unknown if he can reverse it a second time in the case he fails to succeed in changing the timeline the first time.
 * Dreaming: Tsukuyomi theorizes that Sougo's dreams of the future causes him to subconsciously integrate them into the timeline, as evident of the events that transpire in present day while he is dreaming. However, to what extent Sougo has to the control of this ability is unknown. The first recorded usage of this ability was when he dreamt of Rentaro Kagura in the year 2022 and gave rise to Another Shinobi in the present day, The second time was when he dreamt of Rento Makina in 2121 and gave rise to Another Kikai in the present day. However these dreams are not entirely all-powerful, as Sougo can change his present day decisions in order to completely stop or delay the prophesied event from happening, as such when his dreams of the fated duel between him and Geiz on Oma's Day was averted completely.

Weaknesses

 * Poor Academic Performance: According to Tsukuyomi, Sougo is helpless in science and curricular subjects in school. This indicated when he first used the BuildArmor, and instead of proper equations, it simply listed sentences stating that he 'didn't know' or 'something I learned in grade school'. Sougo does however manage to pass his exams with an 82/100 and avoid dropping out, despite having snored through his actual studying. Despite so, Sougo is able to graduate.
 * High Speed Movement: While Zi-O II can perceive future events and prepare an adequate counterattack, this ability can be rendered obsolete against opponents moving at super-speed, as shown with his battle against GeizRevive Shippu.
 * Another Zi-O: While Sougo is able to coexist alongside his Another Rider counterpart, they both also become liable against one another. While Sougo is the only one able to defeat Another Zi-O due to having the corresponding Rider power, Another Zi-O can do the same to Sougo as well under the same circumstances.

Forms
Kamen Rider Zi-O transforms by inserting the Zi-O Ridewatch into the right-hand side of the Ziku-Driver and spinning the Driver 360 degrees. He accesses Rider Armor (ライダーアーマー) forms based on previous Heisei Kamen Riders by inserting Ridewatches into the left-hand side of the Ziku-Driver.

Zi-O can execute a finishing attack known as the Time Break (タイムブレーク) by pressing the Ride-On Starter on their Rider Ridewatch and rotating the Ziku-Driver. Time Breaks performed in a Rider Armor are named after the respective Rider's finishing attacks with "Time Break" after it.

Devices

 * Ziku-Driver - Transformation device
 * Ridewatches - Transformation trinkets
 * Ridewatch Holder - A strap to carry Ridewatches

Weapons
Handheld weapons:
 * Zikan Girade - Zi-O's and Zi-OTrinity's personal weapon and Zi-O II's secondary weapon
 * Ride HeiSaber - Zi-O's personal weapon while using DecadeArmor
 * Saikyo Girade - Zi-O II's and Zi-OTrinity's personal weapon
 * Zikan Zax - Zi-OTrinity's personal weapon
 * Zikan Jaclaw - Zi-OTrinity's personal weapon
 * Zikan Despear - Zi-OTrinity's personal weapon

Suit-equipped weapons:
 * Drill Crusher Crusher - BuildArmor's personal weapon based on the Drill Crusher
 * Gashacon Breaker Breakers - Ex-AidArmor's personal weapons based on the Gashacon Breaker Hammer Mode
 * Booster Module - FourzeArmor's personal weapons based on the Rocket Module

Vehicles

 * Time Mazine

Portrayal
Sougo Tokiwa is portrayed by So Okuno (奥野 壮). As Kamen Rider Zi-O, his suit actor is Seiji Takaiwa (高岩 成二).

Rider No.
As the leading rider protagonist of Kamen Rider Zi-O, Zi-O is labelled Kamen Rider #35 (仮面ライダー35号) and Heisei Rider #20 (平成ライダー20号).

Etymology
Sougo Tokiwa's name is play on, the place where Shotaro Ishinomori lived and started his manga career during 1956 to 1961. "Tokiwa" also carries the word Toki (とき), which can be translated into time when it is written in kanji "時".

"Zi" in Zi-O's name could mean either time (時) or character (字), representing his "watch" and "Katakana" motifs while the "O" means king (王). It may also be for the number 20 (2 - Ji, 0 - Ō), referencing that Zi-O is the 20th Heisei Rider.