Sengoku Driver

"Lock On!"

- Activation announcement

"(word/sound)! (fruit) Arms! (phrase)"

- Transformation announcement

"(word/sound)! (fruit) Squash/Au Lait/Sparking!"

- Finisher announcement

The Sengoku Driver (戦極（センゴク）ドライバー) is the transformation belt for the Armored Riders. It was invented by Ryoma Sengoku of the Yggdrasill Corporation. The Sengoku Driver is the first generation of transformation drivers. The Genesis Driver is the second generation.

Functionality
To transform, the user opens the lock on the Lockseed, then attaches it onto the Drive Bay (ドライブベイ). The Rider then closes the lock to secure it into the Lock On Arm (ロックオンアーム) and presses the Cutting Blade (カッティングブレード) knife down, which cuts open the Lockseed itself.

The Driver announces the Arms granted by the Lockseed, then a giant mechanical piece of fruit corresponding to the Lockseed used appears from a dimensional opening to the Helheim Forest above the user, and falls on top of their head. Once on the user, the fruit forms the helmet, materializes the suit, and the fruit disassembles to form the chestplate and pauldrons, with the Arms Weapon (アームズウェポン) appearing in the Rider's hands once the transformation is complete. If the Rider is already in the Helheim Forest, the fruit would just materialise above the Rider from energy in the same color as the Arms armor is in.

If the wearer of the Sengoku Driver is in danger and has unlocked a Lockseed, the Arms will descend quickly to shield the user from harm.

Even though all the Riders use a Sengoku Driver which share the same voice, they each have a unique Rider Indicator (ライダーインジケーター) plate on the wearer's left hand side. Each Rider Indicator has different voice tones, as well as different phrases for each Lockseed being used. If the Sengoku Driver is destroyed, the Rider Indicator will disappear as well.

Each Sengoku Driver shown originally has a blank plate signifying that it is without a user; this is due to the fact that Sengoku Drivers are designed to synch with the first person that uses them, allowing only that individual to transform from thereon. However, a Yggdrasill Corporation employee was shown wearing a blank Driver with no Cutting Blades attached to the Driver, but the significance of this is unclear, though it could be linked to the fact that the Sengoku Drivers used by the Riders are prototypes and the ones the employees used are the mass-produced versions.

As shown, anyone who wears a Sengoku Driver, be it Riders or Yggdrasill Corporation employees, can turn immature Lockseeds into mature Lockseeds just by picking them from their stems.

The Sengoku Driver can also combine with the Genesis Driver by replacing the former's Rider Indicator with the latter's Genesis Core. Once an Energy Lockseed is inserted, the normal Lockseed is closed. Then, after both Lockseeds are secured, the normal Lockseed's Arms is send upwards into the sky, where it combines with the descending Energy Arms to create a Jinba Arms (ジンバーアームズ), which then falls onto the user once the Cutting Edge is pressed down.

When the Cutting Blade is pressed down between one and three times, a Rider can activate a certain ability:
 * Once: The Squash (スカッシュ) function can either initiate the Rider's Rider Kick or power up the Rider form's Arms Weapon for a finishing attack.
 * Twice: The Au Lait (オーレ) function gives extra power to the Squash function.
 * Thrice: The Sparking (スパーキング) function can either futher enhance a Rider's finishing attack to its full potential or convert the user's armor into its fruit form, which can be used as a shield before it reforms back into armor. For example, Gaim's Orange Arms has the potential to rotate at high speeds when using this function, making any attack thrown at it glance off at an awkward angle, leaving the attacker wide open for a counterattack, while Kurokage's Matsubokkuri Arms spins at an insane speed with his Kagematsu held out.

History
The Sengoku Drivers were invented by Ryoma Sengoku, a scientist of the Yggdrasill Corporation's R&D Branch. As per the company's plans, the first six would be prototypes distributed to the Beat Riders of Zawame City. This way, whenever a Beat Rider transformed and fought, the Driver would collect data that would be used further by the Corporation's R&D Branch. The data collected from the Sengoku Drivers would eventually culminate in the creation of the Genesis Drivers.

Prototype version

 * Kota Kazuraba/Armored Rider Gaim: Found by accident in the Helheim Forest. His Driver was initially purchased from Lock Dealer Sid by Yuya Sumii until the latter devoured a premature Lockseed and turned into an Inves.
 * Kaito Kumon/Armored Rider Baron: Purchased from Sid. During the escape from Yggdrasill Tower, he steals an additional mass-produced version that ends up in the hands of the future Kamen Rider Knuckle.
 * Mitsuzane Kureshima/Armored Rider Ryugen: "Purchased" from Sid. (Used his status to convince Sid into "leaving behind" a Driver).
 * Takatora Kureshima/Armored Rider Zangetsu: Granted to him as head of Yggdrasill's Research and Development. Because of Takatora's early mastery of his Rider powers compared to other Armored Riders, this was presumably the first Sengoku Driver initialized.
 * Hideyasu Jonouchi/Armored Rider Gridon: Purchased from Sid.
 * Ryoji Hase/Armored Rider Kurokage: Purchased from Sid. Broken due to a stray attack by Zangetsu. Deceased.
 * Oren Pierre Alfonzo/Armored Rider Bravo: Confiscated from Sonomura of Team Red Hot. (After initial purchase from Sid)

Mass-produced version

 * Kurokage Troopers: Given to employees of Yggdrasill to function as their foot soldiers.
 * Kamen Rider Knuckle: Unknown, presumably the same model that Kaito stole from Yggdrasill Tower.

Other

 * Bujin Gaim/Armored Rider Bujin Gaim: Unknown. Deceased
 * Ren Aoi/Armored Rider Fifteen: Unknown

Portrayal
The voice of the Sengoku Driver, as well as the Musou Saber and the Lockseeds, is provided by Seiji Hiratoko (平床 政治).