Yuya Sumii

Yuya Sumii (角居 裕也) is the former leader of Team Gaim. He was originally meant to become Kamen Rider Gaim since he was offered the Sengoku Driver from Sid.

History
Originally the leader of Team Gaim, Yuya had trouble with his team during the Inves Games when teams targeted Team Gaim when Yuya himself wasn't present. As an Inves Game user, he had his own Lockseed to call on before giving Mai Takatsukasa her own Lockseed so that she can fend for herself and the team during the Sengoku Era of the Inves Games. When Team Gaim takes a heavy hit and loses their stage, Yuya is confronted by Lock Dealer Sid, who offers him a prototype Sengoku Driver that will allow him to change the days of the Inves Games into something much more. It is presumed he was given the Pine Lockseed because it is the first Sengoku Driver given to the public as his predecessor, Takatora Kureshima used the Melon Lockseed. Yuya tells Kouta about the Sengoku Driver and tells him to meet him, but he is lured into a Crack and is drawn by the Helheim flora and eats one of the fruits, warping his mind and becoming the Byakko Inves while dropping the Sengoku Driver.

When Kouta finds Yuya's Sengoku Driver and puts it on, it also converted the premature Lockseeds into the Orange and Ichigo Lockseeds. Kouta transforms into Gaim for the first time and through the help of the Priestess of Fate, he kills Yuya, never realizing he killed one of his close friends until much later. Yuya's death inspires Kouta to become something much more, someone to never resort to bloodshed, and as a result, Kouta puts blind trust in enemies and friends alike.

In the Soccer Cup event, Kougane masquerades as Yuya and reveals that he isn't Yuya before transforming into Armored Rider Mars and corrupting Kouta.

Yuya would appear in Redyue's illusion with the roles switched up, having Kouta as an Inves and Yuya as Gaim.

Byakko Inves


After Yuya ate a premature lockseed, he transformed into the Byakko Inves (ビャッコインベス), the first Advanced Inves to emerge from the Helheim Forest and attacks Kouta Kazuraba and Mai Takatsukasa, who were ironically were looking for Yuya in the Helheim Forest.
 * Height: 230 cm.
 * Weight: 157 kg.

The Byakko Inves' upper body is covered with a tough shell, protecting it from most attacks, and it uses sharp claws to inflict deadly damage. It also possesses powerful muscles, enabling it to run fast and overpower Kouta when he finds his way into the Helheim Forest, as well as an energy attack that let it fire beams of energy that can slice through practically anything.

It is only after Kouta discovers the purpose of the Orange Lockseed and the Sengoku Driver that Yuya dropped when he ate the premature Lockseed, transforming him into Kamen Rider Gaim, that he is able to defeat the Byakko Inves, ending Yuya's plight.

Arms
Like his fellow Lockseed-using Armored Riders, Kamen Rider Gaim's forms are called Arms (アームズ). His Sengoku Driver plays Japanese horagai music and announces "Soiya" (ソイヤ) before every transformation, except when he transforms into Kiwami Arms, while his personal Lockseeds are styled with a mix of Japanese words and English words. With the exception of Suika Arms, all of Gaim's Japanese Samurai, Ninja, and Shogun-themed Arms' helmets share the title Kabuto (カブト), while his visors are called Pulp Eye (パルプアイ).

By pressing the Sengoku Driver's Cutting Blade down on the Lockseed after transforming from one to three times, Gaim can activate one of three finishing moves based on his current Arms form: Squash (スカッシュ), Au Lait (オーレ), or Sparking (スパーキング). In addition to the Sengoku Driver's finishing moves, Gaim can perform a Fruits Charge (フルーツチャージ) finishing attack by inserting a Lockseed into the Drive Launch of his Musou Saber.

Devices

 * Sengoku Driver - Transformation device
 * Lockseeds - Gives access to Gaim's Arms changes, depending on which lock is used

Weapons

 * Musou Saber - Gaim's side weapon in every single one of his forms
 * Arms Weapons - Weapons that come with the Arms, besides the Musou Saber:
 * Daidaimaru - Gaim Orange Arms' personal weapon

Portrayal
Yuya Sumii is portrayed by Hiromi Sakimoto (崎本 大海).

Legend Rider Lockseeds

 * The following Legend Rider Lockseeds are styled for Gaim, as well as Kurokage, Bujin Gaim, and Kamuro:
 * 1 - "Waza no Ichigō, Let's go!"
 * 2 - "Chikara no Nigō, Let's go!"
 * Riderman - "Kagakusha Met On!"
 * ZX - "Jūgō Cyborg Ninja!
 * Black - "Seiki Oh Black Sun!"
 * Shin - "Kaizou Heishi Level 3!"
 * J - "Shingeki Jumbo Formation!"
 * Shocker - "Jigoku no gundan on Parade! Eeeee!"
 * Great Leader - "Shihaisha of the World!"
 * Shocker Rider Number 1 - "Nise no Hero, Dead Go!"
 * Kabuto - "Ten no Michi My Way!"
 * Den-O - "Iza Climax!"
 * Den-O Climax Form - "Denkamori Climax!"
 * Decade - "Hakaisha on the Road!"
 * Skull - "Otoko-michi Hardboiled!"
 * Fourze - "Seishun Switch On!" (Despite being canonically used by Zangetsu)
 * Wizard - "Shabadoobi Showtime!"
 * Wizard Infinity Style - "Kirakira Infinity!"
 * Gaim - "Fruits Gaim/Yoroi Musha on Parade!"
 * Drive - "Hitoppashiri iza Together!"