As previously reported, Ultimatum will be featuring several guests like Mari Iriki and Kenta Suga. But following the release of Figure Oh, a more detailed cast list has been given.
Other guests include:
- Nao Nagasawa as Haruka Utsugi
- Satoshi Morata as Mr. Morata
- Jinbo Satoshi as Takeshi Satake, Amanogawa’s new principal.
- Kenta Suga as Jiro Kazeda/Sannagiman
- Rika Adachi as Miyoko Ohki
- Kasumi Yamaya as Rumi Komaki
- Toshiya Toyama as Kagehito Banba
- Toshio Furukawa as the voice of Wiseman
 The members of Kamen Rider Club are now doing their own things, Gentaro stayed at Amanogawa and became a teacher. Kengo went on to Kyoto University and is now researching cosmic energy as a graduate student. Yuki finally became an astronaut like she always dreamed of, and Miu has become a model. Shun is now a professional American Football player, Tomoko published several novels as a novelist and JK is working as a journalist.
When the movie starts, Ryusei is working as an Interpol agent together with Inga Blink in South America.
 Miyoko is the only member of the Space Kamen Rider Club. The current club adviser is Gentaro. The two of them are close and have nicknames for each other, Gentaro calls her Miyoppe while Gentaro is called Gen-chan. As the only member, she carries around the club mascot, Hayabusa.
 The Monster Alliance, Daita Kondo, Jiro Kazeda, Rumi Komaki and Chikao Nezu, they wish to create a new Earth with a new superior breed of humans. Jiro is able to transform into Sannagiman by saying “Summon Might Power (Goriki Shorai)”
Kagehito Banba, he supports the Monster Alliance and created a device, Zebar, to enhance ESP powers. In the original Inazuman, Inazuman fought against Emperor Banba, which the name Kagehito Banba is from. In the sequel, Inazuman Flash, Inazuman uses a device called Zebar to generate electricity for his various attacks. The picture on the bottom is the original Zebar, Sannagiman is holding a renewed Zebar in the picture above.
The Hercules Zodiarts relies on strength and uses a club as a weapon. It has the powers of the Twelve Apostles and is capable of summoning Dustards.
Someone has created a device that is able to create an endless amount of monsters. In order to stop this, Haruto heads over to the Underworld. But finds himself in a weird space where people are celebrating Patrine’s birthday. All of a sudden, Ghouls start appearing and attacks the people around. As Haruto is about to transform, Patrine arrives and defeats the Ghouls. Patrine’s real identity is Yu Uemura (上æ‘優), she uses a pendant and says “Cosmo Magic Metamorphose” to transform, just like the original Patrine. The orignal Patrine’s identity was called Yuko Murakami (æ‘上ユウコ), Murakami and Uemura use the same kanji characters, but reversed.
In the movie, Wizard along with Rinko and Shunpei investigate the secrets in the Underworld.