Sougo Tokiwa/Previous Timeline

Sougo Tokiwa (常磐ソウゴ) is the Demon King (魔王) and rules the world in 2068 as Oma Zi-O (オーマジオウ), alternatively spelled Ohma Zi-O.

History
On the day known as Oma's Day, Sougo Tokiwa transformed into Oma Zi-O and he used seven giant monstrous machines called Dai Mazines to destroy the world and became 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, attempted to wage a war against Sougo, only for him to effortlessly destroy them before declaring that none of them were capable of defeating him because he was "born to be king". Some time after this, Tsukuyomi and Geiz traveled to the past, with one intent on changing Sougo's fate of becoming Oma Zi-O and the other wanting to kill him before he can embark on the path.

Meeting his youthful self
One day as he was sitting on his chrysanthemum throne in an isolated field, Sougo sensef his younger self's presence, who had been sent to 2068 by a destroyer of worlds, and pondered if his youthful self wanted to speak to him. He 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 proposed that they talk about the dream they both had in their youth about the Dai Mazines destroying the city, stating every exact detail right down to the man in black who approached them. As the past Sougo realized that Oma Zi-O really was him all along, Sougo stood up as the sudare rose, revealing his face to both his past self and Tsukuyomi. Laughing, Sougo asked his younger self why he was shocked bewildered. He is surprised to find his youthful self to be in denial of becoming the demon king. The past Sougo continued to protest, but Sougo assured him it's their dream and destiny to become king and save the world before telling the past Sougo this was their future. When the past Sougo decreed he would become the "kindest and greatest demon king", Sougo laughed and revealed he swore the same thing, and believed he had actually succeeded. This made the past Sougo enraged, and he decided to defeat him right then and there.

"How nostalgic. So that's how I used to be."

- Oma Zi-O noting Zi-O's strength.

As he watched the past Sougo shove Tsukuyomi aside in anger and transformed into Kamen Rider Zi-O, Sougo laughed as Zi-O executed a Fourze ZureZure Shooting from his Zikan Girade Gun mode. The attack destroyed the throne, but Sougo emerged unscathed, having transformed into Oma Zi-O, which shocked the past Zi-O. Oma Zi-O described his nostalgia, noting that he "used to be this weak", 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 would receive the power of a demon king, but Zi-O dismissed it, transforming into Kamen Rider Zi-O Decade Armor, and performed a Kuuga Dual Time Break Rider Slash with the Ride HeiSaber. Pulling out the Kuuga Ridewatch of his own, Oma Zi-O cancelled Zi-O's attack and countered with Kuuga Rider Kick, sending Zi-O knocking Zi-O down on the ground. Oma Zi-O told his younger self that his indomitable will and refusal to surrender is a quality 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, reducing Zi-O to his knees. Refusing to admit defeat, Zi-O attempted to attack his future self again with a Ryuki Dual Time Break Rider Slash, but Oma Zi-O used his own Ryuki Ridewatch to summon Dragreder and made the dragon attack Zi-O, knocking him back down to the ground once more. Tsukuyomi came to the young Sougo's aid, and Zi-O had become thoroughly overwhelmed by his future self's power, Oma Zi-O offered him a choice: if the past Zi-O did not wish to accept his fate as a malicious demon king, he had to destroy his Ziku-Driver.

Zi-O pondered over this choice, not really wanting to give up his power. 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. He then created a small time window to reveal that Kasshin was overpowering Kamen Rider Geiz Faiz Armor, at the same time stating it would not be long before Geiz was 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 and return to the present. Closing the portal, he expressed his interest in the decision his past self would make. Cancelling his transformation before sitting back on his throne, Sougo sensed his past self's 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 to existence 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 having collected 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 would have to obtain kingship by acquiring 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 GrandZi-O watch and defeated Another Den-O, Oma Zi-O teleported Sougo back to 2068 and forced him in his GrandZi-O form. Standing in front of GrandZi-O, Oma Zi-O congratulated his past incarnate for having successfully obtained all of the Rider powers, but claimed he's still no match for him. GrandZi-O, believing he can fare against his future self, challenged Oma Zi-O. He accepted the challenge and told him to come face his future self as he manifested two Rouze Cards and Double's cyclone energy attacks, which GrandZi-O deflected as he ran towards Oma Zi-O. Face to face, Oma Zi-O traded punches with GrandZi-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 GrandZi-O and resumed their battle, blocking every one of GrandZi-O's attacks with no effort. Despite GrandZi-O's proclamation to end his tyrannic rule after Kuuga and Build's manifestations dissipated, Oma Zi-O reminded him they were still the very same Sougo Tokiwa and scolded his past self for not acknowledging his destiny. This angered GrandZi-O as he summoned a manifestation of Drive. Oma Zi-O took control of the manifestation and corrupted it, forcing it to attack GrandZi-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 hadn't truly acquired all of the Kamen Riders' powers, as young Sougo's Drive Ridewatch was the one Geiz had stolen from Oma Zi-O before. As the past Sougo refused to submit, Oma Zi-O barated his stupidity and fired 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 had altered the timeline, placing his current one in jeopardy if the new one cemented in history. Eventually, his past self was able to return the timeline back to normal, and Oma Zi-O's existence was still untouched.

Aiding Younger Self against Barlckxs
During the Quartzer crisis, he summoned his past self to his era and motivated him to defeat Barlckxs, also revealing that Oma Zi-O is still the 19-year-old Sougo's future not SOUGO's. He later provided his past self with another step towards the ultimate power, the Oma Zi-O Ridewatch.

Zi-O's Final Challenge
"Tell me, what is Oma Zi-O's power?" "The power to destroy time. Someone like Swartz does not have the power to destroy the world. He plans to have you destroy the dimensions." "But I won't become you." "Oh really? You are me. I look forward to seeing... which timeline you destroy and how you go about it."

- Oma Zi-O explaining his power to the past Sougo. After Hiryu Kakogawa's alternate timeline was erased, Oma Zi-O's existence was reestablished in history. Attacking the Resistance, Oma Zi-O forced them into a corner until the past Sougo arrived and transformed into Kamen Rider Zi-O. Relocating to a new field, Oma Zi-O stated he has no recollection of his past self returning to 2068 a second time, which Zi-O assured history changes and what was Oma Zi-O's past is Zi-O's future. Accepting this new event, Oma Zi-O told Zi-O it's pointless to change their history, but Zi-O disagrees and fires his Zikan Girade gun mode at Oma Zi-O, which he deflects with his power and block Zi-O's sword strikes with his arm before seizing his weapon and unleashing an energy wave at Zi-O.

As Zi-O rises, Oma Zi-O saw him transform into Zi-OTrinity and ran forward with the Saikyo Zikan Girade, blocking every strike from the giant blade and the King Giri Giri Slash. Zi-OTrinity rushes forward and brings down the Saikyo Zikan Girade with all his might, which Oma Zi-O countered with his own strength to block it, causing a fallout explosion under the Demon Kings' feet. In a standoff, Oma Zi-O was shocked to see Zi-OTrinity push his arms up and place the sword's tip at his torso, executing a Trinity Time Break Burst Explosion rider slash that sends Oma Zi-O crashing into a wall. Landing back down, a staggering Oma Zi-O admitted he didn't have that kind of power in his own youth, which Zi-OTrinity said his power isn't just his own but his comrades' as well, something Oma Zi-O will never have. Finding Zi-OTrinity's claim amusing, Oma Zi-O surmised that his past self will also sacrifice himself for his friends as well, forcing the past Sougo to cancel his transformation and send both Geiz and Woz back to 2019.

Oma Zi-O then realized the past Sougo doesn't want them to find out about his planned sacrifice as he also admitted that fighting each other is meaningless as he surmised Oma Zi-O has no intention of defeating him as they are both the same person. Hearing the past Sougo's claim to know what his power is, Oma Zi-O revealed it's the power to destroy time and that Swartz is using their power to enact that as the Time Jacker can't do it himself. As his past self still claim he won't become him, Oma Zi-O assures him he will and what choices he will make before sending him back to 2019.

Against his own judgement, Oma Zi-O chose to help his past incarnate and raised his hand and transferred some of his power into a black Ridewatch Tsukuyomi had in her pocket, which Sougo's youthful self slipped into as he saved her from Oma Zi-O's attack, creating the Tsukuyomi Ridewatch for her to use in 2019.

Swartz's Defeat & Oma Zi-O's Finale
After defeating Swartz with the power of Oma Zi-O, the past Sougo visits Oma Zi-O in his throne. Oma Zi-O asks his past self if he really want to discard his dream to become a king, in which the young Sougo answers that he can't fulfill his dream without his friends. Oma Zi-O didn't object to his past self's goal to reset time and looked forward to seeing a future that Sougo would create without the powers of Oma Zi-O.

The young rider then separates and restored the worlds of Kamen Riders back to normal. In the new timeline, Sougo Tokiwa never become a Kamen Rider, thus eliminating Oma Zi-O's existence.

Personality
From what little is known about him, Oma Zi-O was 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 did not even view the resistance fighters as serious threats. His arrogance was not without merit, however, as his battle against his younger self demonstrated impressive mastery over his abilities of his predecessors. Furthermore, he was extremely confident and fearless, as he openly suggested his past self throw away the Ziku-Driver, an action that would result in his own temporal erasure, and even arrogantly laughed as he was disappearing from the timeline, suggesting that everything young Sougo would do were within his calculation and expectation.

However, he still believed that his tyranny had somehow saved the world. When young Sougo claimed that he wished to become the "kindest and greatest" Demon King, this Sougo replied that he did in fact become the "kindest and greatest" Demon King, albeit not in the sense of kindness, but the sense of perfection.

Although known for being a villainous demon king, future Sougo was still shown to have retained some of his past traits. He continued to encourage his younger counterpart to the path to kingship, although it was mostly for saving his own existence. During the Quartzer crisis, he dragged his past self to his era and motivated him to defeat Barlckxs and provided him with another step towards the ultimate power, the Oma Zi-O Ridewatch. He was also quite amused when he found out that Zi-OTrinity could briefly overpower him. He then explained the true extent of his power and gave some of his power to Tsukuyomi, resulting in the creation of the Tsukuyomi Ridewatch.

In the series finale, it was revealed that Oma Zi-O was in fact a version of Sougo who abused his powers and instead turned it into a totalitarian future. When Sougo himself revealed that he was going to use the powers and reset time instead, Oma Zi-O did not get upset, but rather became amused and looked forward to seeing a future that Sougo would create without the powers of Oma Zi-O.

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 senses and identifies 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 attempt to crush Oma Zi-O, he simply uses 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, any disturbance in the timeline (for example, the Ziku-Driver's destruction or Sougo's death) can erase Oma Zi-O's existence.   It is also revealed that Oma Zi-O does not have any intention to go all out against his younger self for this very reason, a fact acknowledged by young Sougo himself after the third match.
 * Lack Of Companionship: In the third match against his younger counterpart, despite the power gap, Oma Zi-O was left overwhelmed by Kamen Rider Zi-OTrinity due to him not having the power of companions alongside him. This allowed his younger counterpart to briefly best him to his knees, although he was probably trying his best not to kill his younger self.
 * Hiryu Kakogawa (formerly): Another Zi-O II's ability to alter history and reality can put Oma Zi-O's existence in jeopardy.

Equipment

 * Oma Zi-O Driver - Transformation device. Oma Zi-O possesses a gold-colored upgrade variant of the Ziku-Driver.
 * 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
As Sougo is an old man at this point in time, he is voiced by Rikiya Koyama (小山 力也), who also voiced the Ziku-Driver. His civilian silhouette is portrayed by Seiji Takaiwa (高岩 成二) His suit actor as Oma Zi-O is Yasuhiko Imai (今井 靖彦).

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)).