Mystery of Naming (ネーミングの謎, Nēmingu no Nazo) is the first episode of Kamen Rider Zi-O: Supplementary Plan. It was released on TTFC accompanying the first episode of Kamen Rider Zi-O, and is referred to as "episode 1.5" of Zi-O. Kamen Rider Zi-O: Supplementary Plan (仮面ライダージオウ 補完計画, Kamen Raidā Jiō Hokan Keikaku) is a TTFC-exclusive miniseries serving as supplementary material to the first 16 episodes of Kamen Rider Zi-O.

Sougo demonstrates how he transforms into Kamen Rider Zi-O and introduces one of his Legend Rider forms: Zi-O BuildArmor.

Geiz demonstrates how he transforms into Kamen Rider Geiz and introduces one of his Legend Rider forms: Geiz GhostArmor.

Sougo Chapter (ソウゴ編, Sougo-hen) is the first installment of Heisei Kamen Rider 20 Series: Supplementary Plan.

Geiz Chapter (ゲイツ編, Geitsu-hen) is the second installment of Heisei Kamen Rider 20 Series: Supplementary Plan.

Tsukuyomi Chapter (ツクヨミ編, Tsukuyomi-hen) is the third installment of Heisei Kamen Rider 20 Series: Supplementary Plan.

Woz Chapter (ウォズ編, Uozu-hen) is the fourth and last installment of Heisei Kamen Rider 20 Series: Supplementary Plan.

"Be the foundation for my becoming the 'King of the World', Kamen Riders..." There is another world different from the world we live in. A man who calls himself "Rider Jacker" has taken hold of the Kamen Riders one after another, stealing their power. Kamen Rider 1 and Black RX rush to save their allies, but they are helpless in the face of the overwhelming power of Rider Jacker, who has overwhelmed the whole world. "We must find the King of the Kamen Rider who will defeat the evil emperor..." Leaving his words, Rider 1 decided to go solely and sent RX to another world. All in order to find the true king and destroy the evil emperor...

A powerful Time Jacker named Tid appears and creates two powerful warriors, Another Double and Another Den-O and orders them to pursue a young boy named Shingo. While Sougo Tokiwa attempts to protect him, he meets a young Kamen Rider fan named Ataru, who demoralizes the existence of the Kamen Riders. What does he mean? Meanwhile, Sento Kiryu attempts to take on Tid alone, but is brainwashed and manipulated by the Time Jacker as a result. With the mystery uncovered, Sougo and Sento head to the Kurogatake Mountains where they must face their true enemy.

Rider Time: Kamen Rider Shinobi (ＲＩＤＥＲ　ＴＩＭＥ 仮面ライダーシノビ, Raida Taimu Kamen Raidā Shinobi) is a three-episode TTFC-exclusive miniseries serving as the first installment of the Zi-O Rider Time series. In the miniseries, Rentaro fights an evil ninja while hiding his identity from his younger sister and rival.

Kamen Rider Zi-O: Special Event (仮面ライダージオウ スペシャルイベント, Kamen Raidā Jiō Supesharu Ibento) is stage show of Kamen Rider Zi-O. The stage show was performed live on May 4-5, 2019, and was released on DVD on September 11, 2019.

The Quartzers, calling themselves the Wardens of Time, appear after Sougo Tokiwa collected all of the Heisei Ridewatches. A grand conspiracy behind the birth of the King of Time becomes clear...

"According to this DVD, it is said that the ghosts of a sister and brother disappeared in this school while playing here. They are still wandering around to find a playing partner, even to this day. And there is one man who awakens in this school tonight. His name is Geiz Myokoin. He has a hidden secret that even no one knows: And that secret is—Oh, don't get cursed from this point on, okay? Now then, please watch what happens next." ―Black Woz

12 years ago, the Daybreak Town Accident changed the world and brought forth a new prosperity towards artificial intelligence. But what if that were to all change? Sougo Tokiwa gave up his conquest for power after he chose to reset the world and live a mundane life. However as a Time Jacker began to alter history once again, Sougo is forced to take up the mantle as Kamen Rider Zi-O once again, as he meets Aruto Hiden, the native Rider of the world he has to save. This is the story of two Kamen Riders from two different worlds, whose fight together will ultimately determine the fate of all reality.

It's September of 2018, and a group of high school students are more than ever excited to pursue their dreams. Sougo Tokiwa wants to become a desirable king, and Keito Myokoin (alternatively called by his friends as Geiz) works tirelessly to become the true judo champion while trying to impress his crush, Alpina Tsukuyomi. However, one day Geiz suffers a career-ending injury during a judo match in a judo tournament, forcing him to give up his dream of become a judo champion. While still grieving, he was met by a mysterious man, who wanted to give Geiz a Ridewatch and a driver. "My name is Woz, I came here to guide you to become a savior. If not, Sougo Tokiwa will become the worst and evillest demon king." Meanwhile, a new transfer student leads him to nothing but one grand conspiracy.

"According to this book, ordinary high school student Sougo Tokiwa is waiting for the future where he becomes the Demon King and Monarch of Time, Ohma Zi-O. Before him lies another SOUGO, who tries to dispose of the unpleasant Heisei era history. Right down to preventing the challenge of being betrayed by me, Woz, Sougo Tokiwa stands up to become the one true king. In short, this is a continuation of the events of the movie--" ―Black Woz

Various people with different backgrounds, including an unusual Sougo Tokiwa, are waking up finding themselves stranded in a house on an isolated island and forced to participate in a death game by a mysterious masked clown. After each round, a loser is killed by a monster emerging from mirrors. As the body count gradually increases, a strange passerby suddenly appears.

The world is ravaged by ravenous monsters and high school students have to fortify themselves in school buildings in order to survive. Various Sougo Tokiwa from different schools, who all can transform into Kamen Rider Zi-O, encounter and fight each other to unveil the true secret of this mysterious situation.