|This article is about a/an transformation device in Kamen Rider W.|
The Lost Driver (ロストドライバー Rosuto Doraibā) is the transformation belt, which is shown used by Kamen Riders Skull, Eternal, and Joker. It is a Second Generation Memory Driver and its design is the same as the Double Driver except it has only one Memory Slot to insert a Gaia Memory.
Due to using refined Gaia Memories that retain their form rather than be absorbed into the user's body, the user is completely shielded from its corrupting effects. This comes at the cost of the Gaia Memory's power being further weakened except for during a Maximum Drive. As it is a prototype that was later developed into the Double Driver, forms accessed with T1 Gaia Memories are extremely weak, though the user's personal experience may mitigate this as shown with Shotaro Hidari's fights after Philip's disappearance.
The Lost Driver was an early attempt by Shroud to further refine the power of the Gaia Memories, after the success of the Gaia Driver. The first known Lost Driver was given to Sokichi Narumi following by Shroud following her escape from the Museum, though he initially refused it on the principle of fighting with his own strength. Sokichi eventually accepted the gift and used it in tandem with the Skull Memory to transform into Kamen Rider Skull. This Driver disappeared along with Sokichi following Phillip's liberation from the Gaia Tower.
The Dummy Dopant would later use the Dummy Gaia Memory to impersonate Sokichi, including replicating his Lost Driver, during the events of Begins Night. Even later, Sokichi's ghost seemingly appeared in front of Shotaro during the events of Kamen Rider W Forever: A to Z/The Gaia Memories of Fate, leaving his Lost Driver to his former protege. Shotaro used the Lost Driver along with the T2 Joker Memory to become Kamen Rider Joker to battle NEVER, though the Driver was seemingly lost before the end of the conflict.
Another identical Lost Driver was used by Jun Kazu and Katsumi Daido to become Kamen Rider Eternal, using both the original and T2 Eternal Memories, though this one was lost following Daido's destruction. After the destruction of the Museum, Shotaro discovers another Lost Driver left behind for him by Phillip, allowing him to continue protecting Futo using his own power. Despite Phillip's return from the True Gaia Memory a year later, Shotaro still carries the Lost Driver with him should he be forced to fight by himself.
By inserting a Gaia Memory into the Memory Slot (メモリスロット Memori Surotto) on the belt buckle, a user can transform into a Kamen Rider.
The transformation into a Kamen Rider will be canceled if a Gaia Memory is removed and not re-inserted for a certain amount of time.
Another slot on the right side of the Lost Driver is called the Maximum Slot (マキシマムスロット Makishimamu Surotto). When a Memory is placed in the Maximum Slot, a Kamen Rider can use a Maximum Drive (マキシマムドライブ Makishimamu Doraibu) finisher attack.
Users (chronological order)
|User||Kamen Rider||Episode Obtained||Episode Destroyed||Description|
|Sokichi Narumi|| ||Skull: Message for W||N/A||Sokichi was given his Lost Driver along with the Skull Gaia Memory by Shroud. Years later, Sokichi's spririt gives his Lost Driver to Shotaro, who used it to become Kamen Rider Joker.|
|Father Roberto Shijima (As the appearance of Sokichi Narumi)|| ||W: Begins Night||N/A||As the Dummy Dopant, the user can assume any form he wishes. Assume Sokichi's form, he can also manifests Lost Driver and Skull Memory automatically, he uses Skull's form to discourage Shotaro's interference.|
|Jun Kazu|| ||Kamen Rider W Returns: Kamen Rider Eternal||N/A|| Jun Kazu was given a Lost Driver and the T1 Eternal Memory by Foundation X, which he used to become Kamen Rider Eternal. However, he was not compatible with the Gaia Memory, so he could only access Eternal's Red Flare Form
After Jun Kazu was killed by Katsumi Daido, his Lost Driver and Gaia Memory were taken by Daido, who became the second Kamen Rider Eternal
|Katsumi Daido|| ||Kamen Rider W Returns: Kamen Rider Eternal||Kamen Rider W Forever: A to Z/The Gaia Memories of Fate|| Daido took Jun Kazu's Lost Driver and T1 Eternal Gaia Memory after killing him and used them to become Kamen Rider Eternal. He later swapped out the T1 Eternal Gaia Memory for its T2 version.
Daido's Lost Driver was presumably destroyed when he was defeated by Kamen Rider Double at the top of Futo Tower
|Philip|| ||Kamen Rider W ~The One Who Continues After Z~||N/A|| When Shotaro had fallen sick and was not able to fight, Shroud gave Philip a Lost Driver to use with his Cyclone Gaia Memory and become Kamen Rider Cyclone. After Shotaro recovers, Philip hides the Lost Driver, intending to not use it again.
After sacrificing his physical body to save Wakana, Philip gives his Lost Driver to Shotaro, who had lost his own, in order for him to become Kamen Rider Joker once again.
|Shotaro Hidari|| || Kamen Rider W Forever: A to Z/The Gaia Memories of Fate
||N/A|| Shotaro was given Sokichi Narumi's Lost Driver by the latter's spirit, which he used with the T2 Joker Gaia Memory that he found to become Kamen Rider Joker. He lost this Driver soon after, however, when he was defeated by Kamen Rider Eternal.
Later, Philip gives his own Lost Driver to Shotaro after he had sacrificed his physical body, enabling Shotaro to become Kamen Rider Joker again with his T1 Joker Gaia Memory
- The Lost Driver is simply a standard Double Driver with the right half of its terminals removed. Nothing replaces the missing terminal, leaving it conspicuously empty.
- It is possible to modify a toy version of the Double Driver by removing its right terminal to create a Lost Driver. An actual Lost Driver toy was released to coincide with the second film, with no changes besides the aforementioned missing right terminal and only including the Skull and Eternal memories. Either of these can be used with the Joker memory, although the Joker Memory included with the Double Driver toy is specifically timed to sound off after the left side memory, resulting in a noticible delay after activation. The T2 Joker Memory toy released as a promotional item for second film does not share this issue.
- It is unknown if the term "Lost" prefix has any particular meaning to the development of the Gaia Memory, as the only known applicable instance was the fact Shroud stole it from the Museum following her escape.