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 as the first generation of Yggdrasill's transformation devices, with the Genesis Driver being 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 and its corresponding phrase, 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 is created when the belt is first put on, locking the belt to that particular user and changing the sounds the belt makes when in use. If the Sengoku Driver is damaged to the point that it will no longer function, the Rider Indicator will return to blank.

Three additional variations on the Sengoku Driver exist, all featuring silver belts rather than the yellow ones of the primary Drivers. The first appears to be a prototype, as it lacks a Cutting Blade or Rider Indicator and thus cannot be used to transform, but can still be used by Yggdrasill Corporation researchers to protect themselves from the hypnotic effects of immature Lockseeds and convert them into mature ones. This type was in use before the events of the show. The second is a full mass-production version of the primary Sengoku Driver, which are used by the Kurokage Troopers. This version lacks a Rider Indicator and does not lock to a user, but instead can be used to transform by anyone. It is implied to be weaker than the primary Drivers by some amount, as seen when Kota and Kaito were able to put up a fight against several Kurokage Troopers without transforming. One such mass-production Driver is also used by Kamen Rider Knuckle. The third variant Sengoku Driver is identical in appearance to the mass-production type but with a Rider Indicator, and is claimed to be stronger than the originals. This type is used by Kamen Rider Bravo and Kamen Rider Gridon from episode 17 onward.

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 activated, the normal Lockseed is closed and unlocked. Then, after the Energy Lockseed is inserted and both Lockseeds are locked in place, the normal Lockseed's Arms is sent upwards into the sky, where it combines with the descending Energy Arms to create a Jimber Arms (ジンバーアームズ), which then falls onto the user as soon as the Cutting Blade 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 temporarily convert the user's armor into its fruit form to be used as a shield.

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, as well as the mass-production Sengoku Drivers used by the Kurokage Troopers.

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 later devoured a premature Lockseed and turned into an Inves, making him drop it for Kota to later find.
 * 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. Later abandoned for the Genesis Driver.
 * 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 Armored Rider Knuckle, Zack.
 * Mitsuzane Kureshima/Armored Rider Ryugen: "Purchased" from Sid via using his dark personality to impress/convince Sid into "accidentally leaving behind" a Driver.
 * Hideyasu Jonouchi/Armored Rider Gridon: Purchased from Sid. Later replaced with an upgraded version with the silver belt of the mass-production model, but still sporting the Rider Indicator. Possibly to remove the lock functions of the belt.
 * 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, who had purchased it from Sid, as he was not worthy of having the Driver, according to Oren. Later replaced with an upgraded version with the silver belt of the mass-production model, but still sporting the Rider Indicator. Possibly to remove the lock functions of the belt.

Mass-produced version

 * Kurokage Troopers: Given to employees of Yggdrasill to function as their foot soldiers.
 * Zack/Armored Rider Knuckle: Received from Kaito after he stepped down as Team Baron's leader.

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).