Souji (ソウジ Sōji) is Souji Tendou's alternative incarnation, and the Kamen Rider Kabuto from the World of Kabuto.
He is a young man who had been given the Kabuto Zecter by the ZECT corporation to be one of its agents in destroying the Worm menace that had befallen his world. However, an encounter with the Phylloxera Worm who mimicked Souji completely, caused the Zecter's Clock Up system to malfunction, trapping Souji in warp speed.
Prior to the start of the Kabuto World arc, Souji encountered the Phylloxera Worm which mimicked his form before he took one of its eyes out with his sister, Mayu, the sole witness before the malfunction occurred. This led to Souji's Worm mimic to become Sou Otogiri, the user of the TheBee Zecter, and led Mayu to hold a grudge against Kabuto, believing that he murdered her brother Souji. However, in spite of being unable to be with her, Souji does everything in his power to protect Mayu while supporting ZECT in exterminating Worms.
However, once deemed a menace by ZECT higher ups, Kabuto is pursued by the group under Otogiri as he commissions the development of a Clock Down System before tricking Mayu to come with her. Eventually, the truth behind Kabuto is revealed as the Clock Down System takes effect when he attempts to save Mayu, who has been revealed to be the Native Sisyra Worm, from Otogiri. After Tsukasa arrives to his aid, the two Riders defeat the Phylloxera Worm while destroying the tower broadcasting the Clock Down waves. Souji slowly disappears back into traveling at the speed of light as Mayu sees him for one last time.
Unlike his counterpart, Souji appears to be more 'down to Earth', and does not seem himself above others. This does not mean that he is not prideful, as he still introduces himself to his opponents with one of his Grandma's speeches. After being trapped in light speed, Souji was kept in solitude from humanity, but chose to bear it to protect his sister, despite the fact that his sister hated him as Kabuto.
- Rider Height: 190cm
- Rider Weight: 132kg
- Ability Perimeters
- Punching Power: 8 tons
- Kicking Power: 10 tons
- Max Jump Height: 20m
- Maximum Running Speed: 100m/8.9s
Kabuto's Masked Form (マスクドフォーム Masukudo Fōmu) is a heavily armored form resembling a pupa with low offensive capabilities. This is the default form that Kabuto transforms into, until he flips the "horn" on the Kabuto Zecter (カブトゼクター Kabuto Zekutā), like a switch, to initiate the Cast Off (キャストオフ Kyasuto Ofu) command. This primes the armor to "Cast Off," when fully activated, sends the armor flying off his form, destroying all lower Worms that get hit with the armor. Kabuto then immediately takes on the sleek Rider Form.
- Rider Height: 195cm
- Rider Weight: 95kg
- Ability Perimeters
- Punching Power: 3 tons
- Kicking Power: 7 tons/19 tons (Rider Kick)
- Max Jump Height: 37m
- Maximum Running Speed: 100m/5.8s
Kabuto's Rider Form (ライダーフォーム Raidā Fōmu) is the sleeker and more offensive-based form which resembles more of a Japanese rhinoceros beetle which Kabuto is named and themed after. In this form, Kabuto has access to the Clock Up (クロックアップ Kurokku Appu) command, enabling Kabuto to travel at near-light speeds to match the speeds of the Worms. By pressing the three buttons on the belt in succession, Kabuto can perform his tachyon-powered Rider Kick (ライダーキック Raidā Kikku). Kabuto Rider Form has three variations of Rider Kick: a normal 180 degree roundhouse kick, a counter kick (360 degree roundhouse kick, which is used to surprise opponents who attempt to attack him from behind), and a flying side kick.
- Rider Height: 198cm
- Rider Weight: 102kg
- Ability Perimeters
- Punching Power: 15 tons
- Kicking Power: 18 tons/35 tons (Rider Kick)
- Maximum Jump Height: 50m
- Maximum running speed: 100m/4.2s
Kabuto is the only Rider from the World of Kabuto that can achieve Hyper Form (ハイパーフォーム Haipā Fōmu), an even stronger version of Rider Form. While Kamen Rider Caucasus stole the Hyper Zecter, he was unable to access a Hyper Form. Accessed through the Hyper Zecter (ハイパーゼクター Haipā Zekutā), a futuristic Zecter made by ZECT, it initiates the Hyper Cast Off (ハイパーキャストオフ Haipā Kyasuto Ofu) command, unleashing its full power. It also has access to Hyper Clock Up (ハイパークロックアップ Haipā Kurokku Appu), a version of Clock Up, able to even time travel due to its faster-than-light speed properties.
Kamen Rider Decade's Final FormRide allows Kabuto to change into Zecter Kabuto (ゼクターカブト Zekutā Kabuto), a giant version of the Kabuto Zecter that flies and can be ridden by Decade. It is able to burrow underground.
- Despite initial thoughts, Souji is the first A.R. Rider to appear in the RPVerse that is used by Tengen.
- Souji is also the only A.R. Rider so far that has a stronger form than his main universe counterpart, with his Hyper Form beating Souji Tendou's version in terms of speed, kicking power, and punching power.