Sengoku Driver

"Lock On!"

- Activation announcement

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

- Transformation announcement

"(word/sound)! (fruit/nut) 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, which causes a dimensional opening into the Helheim Forest to materialize above them and a giant mechanical piece of fruit/nut known as an Armor Part (アーマーパート) that corresponds to the Lockseed used to appear from it. Afterwards, the user attaches the Lockseed onto the Drive Bay (ドライブベイ) and closes the lock to secure it into the Lock On Arm (ロックオンアーム). Finally, the user presses the Cutting Blade (カッティングブレード) knife down, which cuts open the Lockseed itself, causing the Armor Part to fall on top of the user's head and the Driver to announce the Arms granted, along with its corresponding phrase.

Once on the user, the Armor Part materializes the suit and forms the helmet. Afterwards, the Armor Part 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 Armor Part will just materialize 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 Armor Part 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. Wearing a Driver and locking in a mature Lock Seed in also provides nutrition to a wearer thus allowing them to survive without growing hungry.

The Sengoku Driver can also combine with the Genesis Driver by replacing the former's Rider Indicator with the latter's Genesis Core. If the Rider is transformed when they activate an Energy Lockseed, it causes the normal Lockseed to close and unlock. Then, after the Energy Lockseed is inserted and both Lockseeds are locked in place, the normal Lockseed's Armor Part is sent upwards into the sky, where it combines with the Energy Lookseed's descending Armor Part 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. If the Rider is not already transformed, they must lock both Lockseeds in place and press the Cutting Blade down, causing both Lockseed's Armor Parts to descend side by side before being drawn together to combine into the Jimber Arms and fall onto the user as usual.

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 power up a Rider's Arms Weapon for a finishing attack or allow the user to initiate a Rider Kick when infused with the fruit-shaped/nut-shaped energy of their Arms.
 * 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 Part into its original fruit/nut form to spin and use 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.

Ryoma Sengoku reveals that in 10 years time, the day the Inves take over, Yggdrasill can make one billion Sengoku Drivers, wiping out the other six billion people.

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, making him drop it for Kota to later find. This version equips with Musou Saber and its holder, as well as equip with Lock Holder.
 * 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. This version equips with Musou Saber and its holder.
 * Kaito Kumon/Armored Rider Baron: Purchased from Sid; later abandoned for a Genesis Driver. 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. Appears to be yellow belt prototype model. This version equips with Musou Saber and its holder. (Deceased)
 * Ren Aoi/Armored Rider Fifteen: Prior joining Badan Empire after his wife's death. Appears to be silver belt of the mass-production model and sporting the Rider Indicator. Possibly to remove the lock functions of the belt. Received a Musou Saber (but without it's holder) after obtaining the Heisei Rider Lockseed while in Gaim Arms. (Deceased)

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).