Sougo Tokiwa seems like an ordinary high school student, but one thing he has different is that he has dreams of becoming a king! One day, a mysterious young man appeared before him with a prophecy. "Congratulations! Today is a special day for you..." As Sougo is told these words, a giant red robot suddenly appears before him! This robot was a time machine, and Sougo was thrust across various timelines! In the year 2000, the battle of the Heisei Rider's fate, and Sougo's fate in his own birth year, is about to begin...!

Sougo is attacked by a Kamen Rider from the future, Geiz Myokoin, but is saved by a girl from the same future Tsukuyomi, who wishes to help him out. With no clear idea of what is going on, his confusions are further pushed with frequent visits from the mysterious prophet named Woz. Meanwhile Another Build is wreaking havoc, and Sougo discovers that the key to defeating this "Kamen Rider Build" is to meet Sento Kiryu.

Geiz and Tsukuyomi reluctantly collaborate with Sougo, even going as far as to keeping a keen eye on him at school. Meanwhile, a seemingly "unbeatable" game has gone viral amongst the students at Sougo's school, with rumors saying that there is only one person who would be capable of beating it. The three set out to find this rumored genius gamer M, but they encounter an enemy Time Jacker named Ora.

Sougo and the others find Emu Hojo, also known as Kamen Rider Ex-Aid and engage in battle with him. However with the appearance of Another Ex-Aid, Emu memories and powers are stripped from him. Despite so, Sougo needs to somehow gain Emu's trust in order to gain the Ex-Aid Ridewatch and defeat Another Ex-Aid.

Geiz and Tsukuyomi investigate a case of young girls mysteriously disappearing from Amanogawa High School, and are confident that an Another Rider is involved. When their suspicions are proven true, they receive a handful of support from the school's Kamen Rider Club .

With Another Fourze also possessing the powers of Another Faiz, Takumi Inui appears to stop Masato Kusaka and help Sougo investigate the case. As they continue searching for answers behind the mystery of Another Fourze/Faiz's target Karin Yamabuki, they discover a connection with the Ryusei School.

Sougo and the others attend a magic show that was rumored to use real magic instead of just sleight-of-hand tricks, powers that Geiz believes is associated with Kamen Rider Wizard and believe it to be the works of an Another Wizard. Just when Geiz attempts to question the magician, Sougo is...

Tsukuyomi has fallen into a coma thanks to the magic spell that Another Wizard used on her! Geiz, who was wary of Hayase (Another Wizard) since the beginning, tells Sougo off that his kind of approach is what caused Tsukuyomi's coma, as he goes off to save her himself. Just then, Kosuke Nito suddenly appears before him...! Meanwhile, Sougo tries to find the meaning behind Woz's mysterious words...

In the news, the Dan Foundation had declared its independence from the nation of Japan, with its CEO Kuroto Dan proclaiming himself to be a king. Sougo's curiosity with this man leads to the discovery of Kuruto's identity as Another OOO, and Geiz goes back in time to destroy Another Rider at it's source, but Sougo takes a different course of action...

Hina and Eiji were both suddenly captured by King Kuroto Dan! While working together with Hina, Eiji tries to help them escape, which Sougo is trying to prevent! Why is Sougo doing all this? And what is the future that Eiji told him about? Geiz, on the other hand, is more confident now than ever before that Sougo is on the path to become the future's demonic king...

Zi-O fighting... with GaimArmor?! Woz begins his celebration, however, when did Sougo acquire the Gaim Ridewatch? Time proceeds as normal. There are suddenly reports of popular dance team members disappearing one after another. Sougo comes to terms with the fact that Another Rider must be behind these sudden disappearances. However, Sougo seems to be acting somewhat different than usual...

Why are there two Sougos?! Sougo is getting scolded constantly by both Tsukuyomi and Woz. Meanwhile, they start to discover that this other Sougo came from a little farther in the future to travel back in time in order to help Geiz! Being vehemently opposed to Sougo's attempts to rescue Geiz, Woz makes his way towards Swartz's lair...

Geiz was able to return home from Helheim successfully, only now he has a renewed determination to kill Sougo at any time, and anywhere! Another Rider suddenly appears in the city, to be striking people down and taking their souls away! Takeru Tenkuji and Narita of the Mysterious Phenomenon Institute set out to capture this Another Rider, but as soon as they reach the location, they see none other than... Kamen Rider Agito?!

Sougo has become a ghost! His spirit is invisible to both Tsukuyomi and Geiz! In order to return Sougo back to normal, Geiz travels back to the year 2015! Geiz encounters and starts to fight Another Ghost in 2015, but just then, Kamen Rider Decade appears!

Why does Sougo want to become a king in the first place? Sougo starts to tell Tsukuyomi about the continuous dreams he's been having. Just then, a giant event, just like the one in Sougo's dream, suddenly starts to manifest! A giant mecha suddenly appears in the sky! The demonic king's servant from the future, Kasshine suddenly appears! And thanks to Decade's intervention during their fight, Sougo gets blown 50 years into the future...!