After a meteor fall, the evil Rider Poseidon appears from a distortion in space/time. His true identity is Miharu Minato, who fights to protect people 40 years in the future. Miharu transformed with a "Key Ring Machine" and attacks the Riders from the present. Goto and Date are called by Kougami and transform into Birth again. However, against Poseidon, the double Births were in a hopeless battle...
Kamen Rider Aqua
With the power of the water, Miharu transforms into Kamen Rider Aqua to protect the world 40 years into the future. However, he receives a new belt from Kougami and becomes the evil Kamen Rider Poseidon...
A mysterious female student falls from the sky... her name is Nadeshiko Misaki! After catching her, a Zodiarts appears, and Gentaro runs and transforms into Fourze to fight against it, however, Nadeshiko transforms too and they see each other. Who is she?
The members of the Kamen Rider Club are surprised at her appearance, but accept her and decide to work together. However, Gentaro is strange... "That's love." Gentaro falls in love at first sight with Nadeshiko! However, Zodiarts aren't the only ones attacking her. Foundation X, which had antagonized W in the past, also wanted to obtain her power...
An artificially evolved life form by Mutermite.
OOO, Fourze, W and 7 Riders
Meteorites fall around the globe! Rem Kanagi, from Foundation X, obtains a mysterious slime and sets out to obtain Astro Switches and Core Medals.
The 7 Riders were fighting against Foundation X divisions in various countries and gather in Japan to stop his plans! On the other hand, Shotaro and Philip learn about Foundation X's new operation too! Fourze! OOO! W! And the Glorious Seven Riders! The strongest enemy finally appears in the frontlines!
Super evolved life form Mutermite. He hides a horrific real form!