Souji Kusakabe

Souji Kusakabe (日下部 総司 Kusakabe Sōji) is Kamen Rider Dark Kabuto (仮面ライダーダークカブト Kamen Raidā Dāku Kabuto, Masked Rider Dark Kabuto), one of the major antagonists in Kamen Rider Kabuto.

History
Souji Kusakabe is a mimic version of Tendou who was unknowingly captured by Mishima and used for the Hyper Zecter test. It is finally revealed that he is able to use the Dark Kabuto Zecter, a Zecter that mirrors the Kabuto Zecter. His Rider Form is similar to Kabuto's, but he has yellow eyes and his color has changed to black, with the exception of the top of his head, chest, and shoulders which contains dark red circuits which light up upon Cast-Off.

When he is first introduced, he was at the edge of time and space, existing in an unknown universe with Hiyori. Shown in episode 39, he seems to be a kind person that wants to protect Hiyori just as the original Tendou does. His innocence is shown when he observes the flowers and gives off a kind laugh. It is later discovered that he is actually a human that was modified into a Native by Negishi's experiments, in hopes of turning all of humanity into Natives.

When Kabuto is carried to this dimension, the mimic Souji stands by Hiyori defensively, angered by the presence of Kabuto. Calling upon the Dark Kabuto Zecter, he changes into Dark Kabuto and prepares to fight Kabuto. During his first battle, he and Tendou initiate similar Rider Kicks, resulting in Tendou being defeated and flung back to the real world.

Dark Kabuto arrives in the real world through a bolt of lightning, and walks away with a childish look on his face. Later in episode 43, he appears before Kagami and others, stating that he's going to eliminate his other self. The mimic Souji eventually meets the real Tendou and the two engage in battle. The real Souji decides to allow himself to be defeated and thus when Dark Kabuto returns to the universe Hiyori is trapped in, Renge can track the portal and find Hiyori.

When Tendou is on the brink of defeat, Gatack saves him and manages to convince him to fight Dark Kabuto, saying that he cannot allow himself to be defeated like that. Kabuto, now renewed with the will to fight, defeats Dark Kabuto using the Hyper Zecter. However, Hiyori appears after a solar eclipse and says that she is happy to stay with Dark Kabuto in another world. After doing so, Hiyori changes into Sisrya Worm and prepares to protect Dark Kabuto.

After Hiyori and Dark Kabuto return to their dimension, they meet up with Tendou once again, who says that Hiyori should come back. The mimic Souji asks Tendou if he can truly keep his promise of always being by Hiyori's side, and Tendou says he can't. However, he will protect Hiyori for as long as he can, fighting all those who do evil to the world, not because they are Worms. Soon after, Hiyori leaves and abandons Dark Kabuto.

Furious, he arrives in the real world and assaults Hiyori, only to meet two more Reiji Nogis. The Nogis then ask him to cooperate with them, telling Dark Kabuto that he does not know who he truly is. Refusing, Dark Kabuto leaves in a frenzy after attempting to fight the Nogis. After returning to challenge Tendou, he is defeated by Hyper Kabuto. The unconscious mimic Souji is then captured by Mishima once again.

After being tormented by Mishima and Negishi, who both state that he is a failure, he goes into an outrage, attacking Mishima. It is then that they tell this mimic that he was actually a human once, and was altered into a Native. In turn, he was told to mimic Tendou, creating who he is now. They forcefully copied the Kabuto Zecter, creating the Dark Kabuto Zecter, intending to have a powerful force of their own.

During this moment, Tendou appears and uses Clock Up to rescue his mimic. However, the mimic escapes once again, only to meet Mishima once more. As Mishima transforms into Gryllus Worm, the strongest Native, Dark Kabuto charges at him and is defeated.

After Dark Kabuto is captured once again by Mishima, it is revealed that they plan to drain his power and combine it with a fragment of the Native meteorite in order to convert the entirety of humanity into Worms. As Kagami arrives that their secret lab, he is defeated by Mishima and the humans that had become Natives. During the final moments, Dark Kabuto rushes out and captures Negishi, dragging him back into the explosion as Dark Kabuto transforms into a Native. He tells Tendou that he is leaving, and it is up to Tendou to protect this world now.

Personality
Initially shown to be kind, Souji was very much like his counterpart, to the point of wanting to defend Hiyori, only to be angered and saddened by her departure. He is somewhat childish, and will not hesitate to attack anyone who gets in his way, including Hiyori.

Forms
Kamen Rider Dark Kabuto's Masked Form (マスクドフォーム Masukudo Fōmu) is a heavily armored form resembling a pupa that has very little offensive capabilities. This is the default form that Dark Kabuto transforms into, until he flips the "horn" on the Dark Kabuto Zecter, like a switch, to initiate the Cast Off (キャストオフ Kyasuto Ofu) command. Dark Kabuto's Rider Form (ライダーフォーム Raidā Fōmu) is the sleeker and more offensive-based form which more resembles the Japanese rhinoceros beetle on which Dark Kabuto is named after and themed. It is in this form that Dark Kabuto has access to the Clock Up (クロックアップ Kurokku Appu) command which allows Dark Kabuto to travel at near-light speeds to match the speeds of the Worms. By pressing three buttons on the belt in succession, Dark Kabuto can perform his tachyon-powered Rider Kick called the Dark Rider Kick (ダークライダーキック Dāku Raidā Kikku), a roundhouse kick from a standing position.
 * -|Masked Form= Masked Form
 * Height: 190cm
 * Weight: 132kg
 * Ability Perimeters:KRDKA.jpg
 * Punching Power: 8t
 * Kicking Power: 10t
 * Maximum Jump Height: 20m
 * Maximum Running Speed: 100m/8.9s
 * -|Rider Form= Rider Form
 * Rider Height: 195cm
 * Rider Weight: 95kg
 * Ability Perimeters:KRDKAR.jpg
 * Punching Power: 3t
 * Kicking Power: 7t
 * Maximum Jump Height: 37m
 * Maximum Running Speed: 100m/5.8s (Rider Form)
 * Finisher Power: 19t

Trivia

 * Several official sources credit him as either Mimic Souji Tendou (擬態天道 総司 Gitai Tendō Sōji) or just Souji Tendou, just like his original counterpart. However, in the show itself, the character calls himself "Souji Kusakabe" as a way to distinguish himself from Souji Tendou as the person who can be a real brother to Hiyori Kusakabe.