Kamen Rider Eternal (仮面ライダーエターナル Kamen Raidā Etānaru?), set for release on July 21, 2011 (with rentals out on July 8), is primarily a flashback story set before the events of Kamen Rider W Forever: A to Z/The Gaia Memories of Fate.
After taking out a Sweets Dopant, Kamen Rider Double encounters a strange woman who tries to kill the two-in-one Kamen Rider with her psychic powers to avenge Katsumi Daido, the man who almost destroyed Futo. Assuming LunaMetal to restrain her, Shotaro and Philip demand answers on why she would avenge the death of a terrorist. However, upon revealing a harmonica that was his, the psychic reveals that Daido was actually a hero before playing it.
The scene flashes back to Daido's near death experience and conversion by his mother into a Necro-Over. However, after passing every inhumane experimentation, Daido learns that NEVER Project was rejected in favor of the Museum's Gaia Memories. Sometime later, after reviving Reika as the newest member of NEVER, Daido leads his group of six to a country in Southeast Asia to take out a terrorist cell located there without mercy with Reika being tutored by the others in her new life. However, NEVER finds themselves face to face with the psychic as she overwhelms the undead supersoldiers with her powers. Only Daido takes the psychic down, but spares her life. She introduces herself as Mina before a pair of psychic-powered soldiers, Lloyd and Shion, arrive to take Mina back to Doctor Prospect, a Foundation X scientist. Taking Mina with them, they are confronted by Jun Kazu, who assumes the form of Kamen Rider Eternal Red Flare. When Daido touches the Lost Driver, Kazu is forced to eject the incompatible Eternal Memory and uses his psychic power on Daido and Reika before Mina turns herself in.
Coming to, Daido finds himself held hostage by the psychics. He attempts to flee before realizing they are prisoners of Prospect as well. Daido is forced to fight them off before Mina stops them and reveals that they have no choice but to follow Prospect. By then, Prospect arrives and uses his Eyes Memory to put all the psychics, which he calls Quarks, under his control. However, Daido is not intimidated as Prospect becomes the Eyes Dopant and easily overpowers Daido as his body begins to fail him. However, after breaking free from her confinement in the complex, Reika arrives to spirit Daido away. Mina finds Daido's harmonica and tracks Daido down to return it, but accidentally accesses his memories. She reveals that Daido and Reika can not escape as long as the Heaven's Horn barrier is active. Taking Reika's bio-stabilizer at her request, Daido revitalizes himself as he and Reika free the Quarks despite their refusal out of fear. After using his harmonica to calm them down, Daido gives them the drive to rebel before giving Mina the harmonica and going off towards the complex.
As Reika and the Quarks fight off the Foundation X Quarks, Daido makes his way to Prospect's manor where he is confronted by Kazu as he reveals Museum's location in Futo before becoming the Utopia Dopant, stating that he is more compatible with the Utopia Memory. Though no match for the Utopia Dopant, Daido manages to get the Eternal Memory and his perfect synchronization with it allows him to become Kamen Rider Eternal Blue Flare. With his newfound power, Kamen Rider Eternal kills Kazu and destroys Prospect's controls to Heaven's Horn. As the rest of NEVER arrives to take out his soldiers and get the Quarks out, the Eyes Dopant attacks Kamen Rider Eternal before revealing that he will kill all the Quarks with his power. Despite making his way to them, Daido arrives too late to save the Quarks. Mina is the only one left standing until she collapses in his arms. The Eyes Dopant's actions prove to only drive Daido insane as he thanks Prospect for teaching him what Hell truly is before he transforms into Kamen Rider Eternal to send the Eyes Dopant there with the support from his group before he finishes the job with the Eternal Requiem Maximum Drive. As Prospect dies, Daido realizes that the Eternal Memory has been damaged in the fight and he discards it. The maddened Daido decides to stick it to the Museum by going to Futo. However, as Kazu was taken by his fellow Foundation X members to be converted into a Necro-Over, it is revealed that Mina survived the Eyes Dopant's attack.
With her story finished, Shotaro and Philip try to comfort Mina even though she knew the man she loved died that day. As she is taken to the hospital, Shotaro and Philip arrive to the site of their fight with Kamen Rider Eternal to pay their final respects to Daido as now that they understand the method behind his madness.
