The series tells the story of a young man who, according to visitors from the future, is destined to become a tyrant who will subjugate the entire world, and embarks on a journey across time to change his fate; meeting other Kamen Riders from the past along the way.
By Tsukuyomi's request, Geiz delays his plan to kill Sougo as they are both confused as to how a kindly person could become Ohma Zi-O, and they decide to keep watching him for a while by following him closely, even when he is in class.
The three take heed of a mystery related an unbeatable game and several children who played it are now in critical condition in Seito University Hospital, which puts them on the trail of Genius Gamer M. Because of the Time Jackers' interference, another Kamen Rider-like monster was created, erasing all memories of Kamen Rider Ex-Aid from history.
Geiz instructs Sougo not to transform to ensure he doesn't become Ohma Zi-O, and leaves to 2016 to defeat Another Ex-Aid shortly after it was created.
Investigating further in 2018, Sougo discovers that the man who became Another Ex-Aid is attacking small children because his own son has reached a critical stage of an illness and is in need of a heart transplant: their organs are of similar physical size.
Back in 2018, Sougo explains to Geiz and Tsukuyomi that as long as he has them to guide him, he won't become Ohma Zi-O, but instructs them to kill him the moment they both believe he will.
Discovering that the first 4 girls disappeared in 2011 (the year Another Fourze was created), the two Riders journey back in time whilst Tsukuyomi goes in search of Karin.
The Riders learn that Karin died in 2003 in a traffic accident whilst waiting for her friend Sakuma to watch a meteor shower.
By using the Faiz and Fourze Ride Watches, Geiz and Sougo are able to destroy Sakuma's powers, restoring history and allowing Karin to rest in peace.
They learn that in 2012, Hayase gained the power of Another Wizard and moved from back-stage hand to performer to keep the theatre owned by his friend Kaori from closing.
Sougo begins to question Hayase's original motives for gaining the power after saving Kaori from an enraged Another Wizard, whilst Geiz tracks the man with the Ride Watches, Kosuke Nito, who refuses to give them up until he remembers why he has them.
Using the time-crossing abilities of the Faiz Phone-X, Sougo allows the future Hayase to give his younger self words of encouragement to admit his feelings to Kaori.
While investigating him, Sougo and Geiz discover that the Time Jackers are involved as Kuroto has become Another OOO and is converting anyone who defies him into Yummys subserviant to him.
When the Gemn Ride Watch fails to destroy Another OOO in 2016, Tsukuyomi realises that they have the wrong power and year, so return to 2018, where in reaction to Sougo working for King Kuroto, Geiz declares his intent to kill him, but is utterly defeated with ease by Zi-O.
Sougo becomes Kuroto's subordinate and Geiz starts believing that he is indeed following the path to become the tyrant Ohma Zi-O, vowing to destroy him in their next encounter.
3 days earlier, Sougo and co. investigate the mysterious disappearances of popular dance team members, whilst Geiz considers joining the Time Jackers who share the goal of removing Ohma Zi-O.
They soon learn that dance team Baron leader Asura is Another Gaim, and is sending anyone who challenges him to a dark dimension called Helheim Forest.
The second Sougo explains his encounter with the Divine Entity, who told him that he needs to learn to trust and work with others to achieve great things, and was sent him back in time 3 days so he could find a way to save Geiz.
Meanwhile, a new Another Rider that is taking people's souls is being chased by members of a paranormal investigation group including Takeru Tenkuji, and soon Sougo and Geiz are facing off against Another Ghost.
Woz reveals he gave the Time Jackers instructions to create Another Ghost to manipulate history to lure Geiz into getting attacked by Kamen Rider Decade.
Accepting and swearing his fate to become the demon king who will save the world, Sougo transforms into Zi-O and using Decade and Ex-Aids power, forces Tsukasa to pull back and destroys the Assassin.
Sougo and Geiz face a new Another Rider who can reflect all attacks against it with two times the power, and their investigation leads them to meet Daisuke Okubo, chief editor of the ORE Journal.
Geiz reaffirms his intention to stop Sougo from becoming Ohma Zi-O, but Black Woz allies himself with Heure to intervene in the fight between the two Kamen Riders.
When Sougo's group faces a stronger Another Agito to restore his victims to normal, Tsukuyomi appears to unlock a mysterious power hidden within herself.
As Sougo's birthday arrives, he approaches Kyosuke Kiriya for Kamen Rider Hibiki's powers, but the latter reveals that he had never truly surpassed his teacher.
Finally aware of who Another Kiva is, Sougo approaches her in an attempt to make amends just as the Time Jackers try to form an alliance with her to stop Kamen Rider Ginga.
With Another Drive's identity supposedly revealed, Geiz argues with Sougo over both trusting Heure and Ora while questioning if he has any right to remain in the present.
With Tsukasa's powers, Tsukuyomi takes Sougo to her original timeline to investigate as an army of Roidmudes led by Mashin Chaser stand in their way.
Worlds and his friends continue to fight Swartz and the influx of past monsters, Sougo realizes he is the epicenter of the chaos and travels to 2068 to settle things with Ohma Zi-O in a final confrontation.
Following the battle's end, Woz congratulates and pledges his loyalty to Ohma Zi-O, but Sougo relinquishes his powers to undo the damage done.