Sougo Tokiwa/Previous Timeline

Sougo Tokiwa (常磐ソウゴ) is the future version of his present day self who rules the Earth in 2068 as Oma Zi-O (オーマジオウ), alternatively spelled Ohma Zi-O, and also referred to as the Demon King (魔王) by the characters of the series.

History
At some point, Sougo Tokiwa acquired the white half of the Zi-O Ridewatch II and completed it using its Mirror World Part. On the day known as Oma's Day, the Ridewatch triggered his transformation into Oma Zi-O and used seven giant monstrous machines called Dai Mazines to destroy the world and become the revered "Demon King." Oma Zi-O was the original owner of the Ridewatches of Kamen Riders Drive and Ghost before they were stolen by Geiz.

At the start of the series, Tsukuyomi and Geiz, along with the Resistance, are attempting to wage a battle against Sougo, only for him to effortlessly destroy them utterly before declaring that none of them were capable of defeating him because he was born to be king. Sometime after this, Tsukuyomi and Geiz traveled to the past, one intent on changing Sougo's fate of becoming Oma Zi-O and the other attempting to kill him before he can embark on the path.

Meeting his youthful self
One day as he sat in his chrysanthemum throne in an isolated field, Sougo sensed his younger self, who was sent to 2068 by a destroyer of worlds, and ponders if his youthful self wanted to speak to him. Reaching his decision, Sougo utilized the Ryuki RideWatch and summoned Dragreder to bring both his past self and Tsukuyomi to him. As the past Sougo spotted him but unsure of his identity, Sougo told him they'll talk about the dream they've both had in their youth about the Dai Mazine destroying the city, stating every exact detail right down to the man who approached them. As the past Sougo realized who it was, Sougo stood up as the sudare rises, revealing his face to both his past self and Tsukuyomi. Laughing, Sougo asked his younger self why he was shocked and surmised his youthful self was in denial about becoming the demon king. The past Sougo continues to protest, but Sougo assured him it's their dream to become king and save the world before telling the past Sougo this is their future. Even when the past Sougo decreed he'll become the kind and greatest demon king, Sougo laughed and revealed it his thought as well, which made the past Sougo decide to defeat him now.

As he watched the past Sougo shove Tsukuyomi aside and transformed into Kamen Rider Zi-O, Sougo laughed as Zi-O executed a Fourze Suresure Shooting from his Zikan Girade Gun mode. The attack destroyed the throne, but Sougo emerged unscathed by transforming into Oma Zi-O, which shocked the past Zi-O while Oma Zi-O described the nostalgia before countering with a golden shockwave, sending Zi-O flying through the dirt. Approaching Zi-O, Oma Zi-O assured him at some point in his time, he'll receive the power of a demon king, but Zi-O dismissed it, transformed into Kamen Rider Zi-O Decade Armor, and performed a Kuuga Dual Time Break Rider slash with the HeiSaber. Pulling out the Kuuga Ridewatch, Oma Zi-O cancelled Zi-O's attack and countered with Kuuga Rider kick, sending Zi-O back on the ground. Oma Zi-O told his younger self the indomitable will is a sign of a king, but Zi-O told him to shut up and executed a Kiva Dual Time Break, which was countered by Oma Zi-O's Kiva-based dark energy bats summoned via Kiva Ridewatch, knocking Zi-O to his knees. Refusing to accept defeat, Zi-O attempted to attack his future self with a Ryuki Dual Time Break Rider slash, but Oma Zi-O used the Ryuki Ridewatch to summon Dragreder and made the dragon attack Zi-O, knocking him back on the dirt. As Tsukuyomi moved closer and Zi-O became overwhelmed by his future self's strength, Oma Zi-O offered him a choice: if the past Zi-O refuses to accept his fate as a malicious demon king, he must destroy his Ziku-Driver.

As Zi-O pondered over this choice, Oma Zi-O generated golden energy from his clock hand-style cape and launched it at Zi-O, drawing the rider closer before detonating it and forcing the past Sougo out of his transformation. After Tsukuyomi ran to the past Sougo's side, Oma Zi-O created a small time window to reveal Kasshin overpowering Kamen Rider Geiz Faiz Armor, stating it won't be long before Geiz is killed. Telling the past Sougo to return to 2018, Oma Zi-O created a time portal and allowed both his past self and Tsukuyomi to pass through it before closing the portal and announced his interest in which decision his past self will make. Cancelling his transformation before sitting back on his throne, Sougo sensed his past self letting Geiz destroy his Ziku-Driver and laughed as he was erased from the timeline. After the past Sougo, despite knowing the horror of becoming the demon king, became Kamen Rider Zi-O again, Sougo was restored back in the timeline, laughing as he knew his past self couldn't give up his dream.

Message from the Future
"There are six powers left for you to obtain. Obtaining all the watches is... your path towards kingship. The path to conquest!"

- Oma Zi-O presenting his past self the final Ridewatches to become the Demon King. After the past Sougo acquired the power of Trinity and the Blade Ridewatch, Daiki Kaito presented Sougo and Geiz with a message from Oma Zi-O, who congratulated his past self for collecting the Blade Ridewatch. Oma Zi-O then manifested six Ridewatches: Agito, Hibiki, Kabuto, Den-O, Kiva, and Drive, and told the past Sougo that he will obtain kingship and the path of conquest once he acquire the remaining six Rider powers.

Duel of the Demon Kings & Time Alteration
"My youthful self." "Oma Zi-O." "So you've obtained the power of all the Riders. Regardless, you're still no match for me." "Let's see. I've got a feeling this is going to work out."

- Oma Zi-O challenging his past incarnate to test his new power. After his past self obtained the Grand Zi-O watch and defeated Another Den-O, Oma Zi-O teleported Sougo back to 2068 and forced him in his Grand Zi-O form. Standing in front of Grand Zi-O, Oma Zi-O congratulated his past incarnate for obtain all of the Rider powers, but claimed he's still no match for him. Grand Zi-O, believing he can fare against his future self, challenged Oma Zi-O, which he accepted and told him to come as he manifested two Rouze Cards and Double's cyclone energy attacks, which Grand Zi-O deflected as he ran at Oma Zi-O. Face to face, Oma Zi-O traded punches with Grand Zi-O before both riders forced one another back and summoned manifestations of Kamen Riders Kuuga and Build. As the manifestations fought, Oma Zi-O teleported in front of Grand Zi-O and resumed their battle, blocking every one of Grand Zi-O's attacks with no effort. Despite Grand Zi-O's proclamation to end his tyrannic rule after Kuuga and Build's manifestations dissipated, Oma Zi-O reminds him they're still Sougo Tokiwa and scolds his past self for not acknowledging his destiny, angering Grand Zi-O as he summoned a manifestation of Drive. Oma Zi-O took control of the manifestation and corrupted it, forcing it to attack Grand Zi-O and defeat him with a Full Throttle Rider kick, cancelling the past Sougo's transformation.

As Woz teleported and rushed to the past Sougo's side, who wondered why he lost, Oma Zi-O told him he hasn't truly acquired all of the Kamen Riders' powers as the Drive Ridewatch was the one Geiz stole from Oma Zi-O. As the past Sougo refuses to submit, Oma Zi-O scolds his stupidity and fires a shockwave at his past incarnate, forcing Woz to send the past Sougo back to 2019. Oma Zi-O commended Woz for his action as the Drive manifestation dissipated and chronal energy surged through 2068. Oma Zi-O realized that someone in the past altered the timeline, placing his current one in jeopardy if the new one cements in history.

Personality
From what little is known about him, Oma Zi-O is shown to be very arrogant due to his tremendous power, proclaiming that he was chosen to be the ruler of the world from birth. He does not even view the resistance fighters as serious threats. His arrogance is not without merit, however, as his battle against his younger self demonstrates impressive mastery over his abilities of his predecessors. Furthermore, he is extremely confident and fearless, as he openly suggests his past self to throw away the Ziku-Driver, an action would result in his own temporal erasure, and even arrogantly laughed as he is disappearing from the timeline, suggesting that everything young Sougo would do are within his calculation and expectation.

However, he apparently still believes that his tyranny has somehow saved the world. When young Sougo claims that he wishes to become the greatest Demon King, this Sougo replies that he did become the greatest Demon King, not in the sense of kindness, but in the sense of perfection.

Powers & Abilities

 * Disintegration: Oma Zi-O can send out a powerful wave of energy that can disintegrate anything in its path.
 * Enhanced Awareness: Oma Zi-O immediately sensed and identified the threat of incoming missiles.
 * Velocity Manipulation: It is shown that Oma Zi-O can freeze dozens of missiles.
 * Time Manipulation: Oma Zi-O can freeze time before he can disintegrate enemies. According to Tsukuyomi, Oma Zi-O has all of the abilities that come with Sougo Tokiwa's Zi-O Ridewatch II, thus implying that Oma Zi-O can reverse time as well.
 * Timeline Alteration: Tsukuyomi theorizes that Sougo's dreaming ability causes his encounters with the future Riders to actually happen in reality, an ability that according to her, Oma Zi-O also seems to possess.
 * Telekinesis: When an army of Time Mazines tried to crush Oma Zi-O, he simply used telekinesis to hurl them into each other.
 * Time Portal Creation: Oma Zi-O can create time portals, which are even capable of forcefully pulling a person into themselves.
 * Keen Manipulator: Like his past iteration, the future Sougo is also manipulative, even towards his younger self.
 * Legend Riders' Powers: Oma Zi-O has the powers of all the Riders prior to the year 2068. He can tap into their powers by activating their Ridewatches as well as simply through his will. He can also summon Rider clones and even corrupt the ones summoned by others.
 * Kuuga: Summons an energy construct of Linto Hieroglyphics to create an energy kick.
 * Kiva: Summons a colony of energy bats.
 * Ryuki: Summons Dragreder to attack his target.
 * Blade: Summons two large Rouze Cards to attack his target.
 * Double: Summons a green/purple colored energy cyclone.

Weaknesses

 * Sougo Tokiwa: Because Oma Zi-O is Sougo's future self, Oma Zi-O will be erased from existence if Sougo's Ziku Driver is destroyed, and will stay erased until Sougo receives a new one. Granted, Oma Zi-O will also vanish from existence if Sougo dies as well.
 * Hiryu Kakogawa (formerly): Because of Another Zi-O II's powers to alter time itself, it could put Oma Zi-O's existence in jeopardy.

Equipment

 * Ziku-Driver - Transformation device. Oma Zi-O possesses a gold-colored and possibly modified variant of it.
 * Ridewatch Holder - Oma Zi-O possesses a gold-colored variant of this.
 * Ridewatches - Transformation trinkets. He was in possession of at least the Ghost and Drive Ridewatches before being stolen by Geiz. He currently is seen to be in possession of the Kuuga, Kiva, and Ryuki Ridewatches (of his time).
 * Dragreder - Ryuki's Contract Monster, summoned through the Ryuki Ridewatch.

Portrayal
Being the future counterpart of Sougo Tokiwa, he is portrayed by an uncredited actor. As Oma Zi-O, he is voiced by Rikiya Koyama (小山 力也), who also voiced the Ziku-Driver. His suit actor is Seiji Takaiwa (高岩 成二) and Yasuhiko Imai (今井 靖彦) early in the series.

Etymology
The "Oma" in his name refers to (逢魔時) in Japanese mythology and also a reversed spelling of Demon King (魔王(マオー)).

Appearances

 * Icon-zi-o.png Kamen Rider Zi-O
 * Episode 1: Kingdom 2068
 * Episode 15: Back to 2068
 * Episode 16: Forever King 2018
 * Episode 17: Happy New Woz 2019
 * Episode 29: Blade Joker!? 2019
 * Episode 30: 2019: Trinity Has Begun!
 * Episode 40: 2017: Grand Climax!
 * Episode 41: 2019: World, Reset
 * Kamen Rider Zi-O: Over Quartzer
 * Episode 48: 2068: Oma Time