Sengoku Driver

"Lock On!"

- Activation announcement

"(word/guitar riff)! (fruit/nut) Arms! (phrase)"

- Transformation announcement

"(word/guitar riff)! (fruit/nut) Squash/Au Lait/Sparking!"

- Finisher announcement

"Lock Off!"

- Deactivation 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.

In theory, an indefinite amount of Sengoku Drivers exist, as there were numerous people (Fifteen, Bujin Gaim, Mars) who received Sengoku Drivers via unconventional means.

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 an Armor Part that corresponds to the Lockseed used to appear from it. Afterwards, the user attaches the Lockseed onto the belt's 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 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.

Four 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 Kouta and Kaito were able to put up a fight against several Kurokage Troopers without transforming. A third, different variation of the mass-production Driver is found on Ryoma Sengoku's desk and is later used by Kamen Rider Knuckle, utilizing a slightly different Pre-Arms base suit than the Kurokage Troopers (the head/helmet is different). The fourth 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 and used by Kamen Rider Gaim Yami in the movie in conjunction with the Genesis Core in place of the Rider Indicator.

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 merges with the Energy Lookseed's descending Armor Part to become the jinbaori-themed Jimber Armor Part, which then falls onto the Rider as soon as the Cutting Blade is pressed down, allowing them to assume Jimber Arms. 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 Armor Part 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 further 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. Unfortunately, the Over Lords sped it up thanks to Rosyuo and Yggdrasill's self-destruction.

Since the death of Ryoma Sengoku, Kaito Kumon has taken up the means of power by becoming an Over Lord. Using this new found power, he advances his goal of destroying the world. However many Armored Riders have tried to face him, resulting in defeat and destroyed Sengoku Drivers.

Prototype version

 * Kouta Kazuraba/Armored Rider Gaim: A unit that equips the user with a Musou Saber, its holder and a Lock Holder. In Kiwami Arms, a second Lock Holder (which Kouta uses for his Energy Lockseeds) replaces the Musou Saber and its holder. One of the six Drivers purchased from Lock Dealer Sid; its original owner was Yuya Sumii, but after entering the Helheim Forest and eating a premature Lockseed, he was turned into the Byakko Inves and dropped the Driver under a tree, where Kouta would later find it and take it for his own use.
 * Takatora Kureshima/Armored Rider Zangetsu: A unit that equips the user with a Musou Saber and its holder. Granted to him as the head of Yggdrasill's Research and Development, and was presumably the first Sengoku Driver to be initialized. In its first use, it failed badly, leaving his shoulder scarred; the belt was later upgraded into its current form. He later retired its use in favor of his new Genesis Driver; when that Driver was taken from him, he reclaimed his original unit and began using it again. It was subsequently destroyed in battle against Mitsuzane as Zangetsu Shin; Takatora himself fell into the sea as a result. (User MIA.)
 * Kaito Kumon/Armored Rider Baron: A unit with no special attachments; one of the six Drivers purchased from Sid. Later began swapping it out for a new Genesis Driver as necessary. Kaito also stole a mass-production driver from Ryoma Sengoku's office during his escape from Yggdrasill Tower, and gave it to Zack, the future Armored Rider Knuckle.
 * Mitsuzane Kureshima/Armored Rider Ryugen: A unit with no special attachments; one of the six Drivers "purchased" from Sid, with Mitsuzane using his dark personality to impress/convince Sid into "accidentally leaving behind" a Driver. He later retired it in favor of his brother's Genesis Driver, but returned to using his original Driver after acquiring the Yometsuheguri Lockseed, its use altering the design of his Rider Indicator.
 * Hideyasu Jonouchi/Armored Rider Gridon: A unit with no special attachments; one of the six Drivers purchased from Sid. Later retired its use in favor of a mass-production unit.
 * Ryoji Hase/Armored Rider Kurokage: A unit with no special attachments; one of the six Drivers purchased from Sid. It was later destroyed in battle with Zangetsu. (User deceased as a result of a later battle.)
 * Oren Pierre Alfonzo/Armored Rider Bravo: A unit with no special attachments; one of the six Drivers purchased from Sid. Its original owner was Sonomura of Team Red Hot, but Oren confiscated it from him, both for causing a disturbance in his pastry shop and because Oren felt Sonamura was not worthy of having it. Later retired its use in favor of a mass-production unit.

Mass-produced version

 * Kurokage Troopers: Units with no special attachments; used by employees of Yggdrasill to function as their foot soldiers.
 * Yggdrasill Corporation Research Members: Harvesting Driver units with no Cutting Blade or special attachments; used by employees of Yggdrasil to safely harvest Lockseeds.
 * Takatora Kureshima: Harvesting Driver unit with no Cutting Blade or special attachments; given to him by Rosyuo after he lost his Genesis Driver and was trapped in the Helheim Forest.
 * Zack/Armored Rider Knuckle: A unit with no special attachments; stolen from Ryoma Sengoku's office in Yggdrasill Tower by Kaito, who gave it to Zack after stepping down as Team Baron's leader. It was later destroyed in battle with Baron.
 * Hideyasu Jonouchi/Armored Rider Gridon: A new unit with Gridon's original Rider Indicator (most likely to identify the Pre-Arms Suit); given to him after becoming an employee of Yggdrasill. It was later destroyed in battle by Knuckle and Marika.
 * Oren Pierre Alfonzo/Armored Rider Bravo: A new unit with Bravo's original Rider Indicator (most likely to identify the Pre-Arms Suit); given to him after becoming an employee of Yggdrasill. It was later destroyed in battle by Lord Baron.

Other

 * Bujin Rider Gaim: Aesthetically identical to the yellow-belted prototype models (including a unique Rider Indicator), this unit equips the user with a Musou Saber and its holder; how he got it is unknown. Destroyed along with Bujin Gaim himself. (Deceased)
 * Ren Aoi/Armored Rider Fifteen: Aesthetically identical to the silver-belted mass production models, but with a unique Rider Indicator and belt formation (it appears to be made out of bone at first, then solidifies into a standard silver belt); obtained prior to joining the Badan Empire after his son's apparent death. Destroyed by Gaim 1 Arms, freeing him from Badan's brainwashing.
 * Kougane/Armored Rider Mars: Aesthetically identical to the yellow-belted prototype models (including a unique Rider Indicator) but with no special attachments; appeared on him when he was awoken in Soccer World by the alternate Ryoma Sengoku. Destroyed along with Mars himself. (Deceased)
 * Lapis/Armored Rider Kamuro: Aesthetically identical to the yellow-belted prototype models (including a unique Rider Indicator) but with no special attachments; given to him by DJ Sagara for a short time to fight Mars. (User MIA.)
 * Kouta Kazuraba/Armored Rider Gaim Yami: Aesthetically identical to the silver-belted mass production models, but with a Genesis Core in place of a Rider Indicator, this unit equips the user with a Lock Holder; given to him by Kougane after being defeated and brainwashed by him. Removed/destroyed when he was freed from Kougane's control.
 * Yuya Sumii/Armored Rider Gaim: A unit that equips the user with a Musou Saber, its holder and a Lock Holder; one of the six prototype Drivers purchased from Sid. In Kouta's vision of an alternate timeline, Yuya had successfully used this Driver to become Gaim and fought Kouta, who had become the Byakko Inves in his stead.
 * Armored Rider Jam: Aesthetically identical to the yellow-belted prototype models (including a unique Rider Indicator).

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).