|This article is about a/an event in Kamen Rider Zi-O.|
Throughout the series, it had been established from the very beginning that Sougo Tokiwa will inevitably become Kamen Rider Ohma Zi-O, which that day will be known as Oma's Day (オーマの日 Ōma no Hi), alternatively spelled as Oma's Day. While several efforts had been made in an attempt to prevent this fateful day from happening, it only delayed the event and created several different timelines in the space-time continuum, each with its own version on how it happened.
- "Sometime in the future, an event known as Oma's Day happens. On that day, you became Ohma Zi-O and all the Riders aside from you disappear."
- ―Geiz explaining Oma's Day to Sougo[src]
In the original timeline, on April 17, 2019, Sougo Tokiwa obtained the Zi-O II Ridewatch and evolved from his base form into the demonic Kamen Rider Ohma Zi-O, eventually using his powers to wipe out all the Kamen Riders and at least 50% of the Earth's population. By 2068, the Resistance was formed to combat against Ohma Zi-O's totalitarian dystopia, with Geiz and Tsukuyomi desperately going back to 2018 in order to alter this dire future. However, Woz followed them through in an effort to stop them, although he later enters a feud against his white counterpart in an attempt to secure their own futures.
- "On the upcoming Oma's Day, you will destroy Ohma Zi-O, and become the one to change history!"
- ―White Woz revealing the newly diverged Oma's Day to Geiz and Sougo[src]
Due to the present day Zi-O temporarily giving up his Ziku-Driver, it created a diverging future where Geiz defeated Zi-O and became known as Kamen Rider GeizRevive, the world's savior. From this future, White Woz traveled to January of 2019 to ensure that this timeline is set in stone, eventually entering a feud with his black counterpart to secure their timelines. Due to this, new Kamen Riders are able to rise, as such Kamen Rider Quiz in 2040. White Woz describes this timeline to be "at peace, like time itself has stopped".
It is never explicitly stated whether Sougo is alive or not in this timeline.
Because of the multiple alterations to the timeline caused by several variables from the future, this event was pushed back several times, negating the above timelines and creating an entirely new one instead.
The Duel Between Zi-O and Geiz Averted
- Sougo destroyed his Ziku Driver after affirming his own future as Ohma Zi-O, but Geiz convinced him to try to become a good king instead. This created a divergent future where Zi-O was defeated by Geiz in a duel, later obtaining the power of GeizRevive as the world's savior. From this reality, White Woz traveled to the present day to make sure his future was set in stone.
- Sougo traveled to the Mirror World and overcomes the tormenting inflicted upon him by his Mirror World counterpart, granting him the power of Zi-O II. This allowed him to unconsciously have prophetic dreams of the future and make it reality, with one dream being the duel between him and Geiz, which resulted in his own loss that brought White Woz to their timeline.
- Due to White Woz's interference from the future, Geiz had attained his GeizRevive form much earlier than prophesized, thus his continued over-usage of the form made him weaker to the point where he may not survive.
- By stealing the Kamen Rider Woz powers from White Woz to prevent him from fighting, Black Woz was able to use them and prevent the duel from happening instead. Tsukuyomi returned from the future and helped Sougo and Geiz reconcile, affectively nulling the duel completely.
- With his plan foiled and being unable to secure his own future, White Woz manipulated the Joker Undead out of hiding to restart the Battle Fight and destroy the world completely.
- Sougo convinced White Woz to not give up fighting for his own beliefs and willingly drop his malicious plans, though the Battle Fight was still raging. Sougo combines his powers with Geiz and Woz, forming Zi-OTrinity in order to stop Another Blade and bring an end to the Battle Fight. As a result, White Woz was erased from existence and Oma's Day was pushed back.
The Path Towards GrandZi-O and Beyond
- With his future as Ohma Zi-O revealed to still be intact, Sougo ventures on a journey to collect the six remaining Ridewatches and complete the GrandZi-O Ridewatch. Knowing he did not faithfully have the Drive Watch, Sougo recklessly challenges Ohma Zi-O to a duel in 2068, which allowed Hiryu Kakogawa to jeopardize both of their existences by altering reality in 2019.
- Michal Minato is forced to intervene from 2050 to warn the team of their actions that are causing a temporal loop, allowing the coming apocalypse they've been trying to prevent to happen.
The Path Towards Ohma Zi-O
- In the midst of the temporal disruption, Swartz is successful in stealing Tsukasa Kadoya's powers. Using Another Decade's powers, he began to merge every single reality together, ultimately shattering the Ridewatches.
- The team met with Go Shijima and Krim Steinbelt to acquire the Drive and Mach Ridewatches, and faced Quartzer where they learn of Black Woz's true origins. After Sougo attained Ohma Form, Geiz and Tsukuyomi were erased from existence. However because of Swartz's merger in the true timeline, the two are revived and Ohma Form is erased from existence instead.
- To break the time loop that created Ohma Zi-O, Sougo travels to 2068 and provides the "past" Tsukuyomi with her own Ridewatch, allowing her present-day self to become Kamen Rider Tsukuyomi. Using her new powers, she feigns loyalty to Swartz in order to discover his true intentions.
- Junichiro repairs the Ridewatches and Sougo enters his final showdown with Swartz. Geiz is killed in the process, triggering Sougo's transformation into Ohma Zi-O. After Tsukuyomi is killed as well, Sougo mercilessly kills Swartz, later deciding to rewrite the world rather than rule it. At this point in time, the Ohma Zi-O from 2068 vanishes from existence as peace and stability is restored to the world.
To be added.