Soji Tendo, the Kabuto Zecter's wearer, is a mysterious 21-year old man who often seems to follow monk-like philosophies of peace. Tendo often says zen-like phrases he apparently learned from his grandmother. The name Tendou came from his grandmother who took him in after his real parents died, and that his real name was Souji Kusakabe. Tendo has no actual job because he believes that he is destined for something bigger, which is becoming Kabuto. Despite having many talents such as cooking to hairstyling to excelling at various sports, but he seemed uninterested in them. Tendo lives at home with his little sister Juka. Tendo is somewhat rude, and exceedingly arrogant at first glance and this holds back the caring emotions he has for others. His feelings for his two sisters are among the few things that can break his serious demeanor. Soji's parents were actually murdered and mimicked by Natives, at the time his mother was pregnant, years before the Worms arrived on Earth, and although the original Hiyori Kusakabe died with them before birth she was soon 'reborn' as a Native/Worm.
He possesses an uncanny ability to see through the Worms' disguises or any nearby. After defeating Kageyama and seeing him as unfit to be a leader, he joins ZECT, which was to locate some Worms and then quits. Tendou possesses powerful strength and is stronger than any other Riders. Kabuto uses a partial Put-On after fighting Sasword, with him winning. A Hyper Kabuto from the future arrived and orchestrated a plan with Tendou to fake Hiyori's death, which worked temporarily. Tendou reveals to Hiyori that they are related. He met his parents as Worms again on the day of the Shibuya accident. He had planned to take revenge on them but once he saw Hiyori, he changed his mind and decided to save her. Tendou discovers Kagami spying on their conversation and asks Kagami which side will he stand on. Hiyori however, is attracted to Area X by the man in the iron mask, who was previously a test subject of the Hyper Zecter. The Zecter went out of control, flinging both of them to the edge of time and space. Tendou collects all the Zecters as he believes the only way to save Hiyori and to ensure that he is the only Rider. He obtains the TheBee Zecter after Kick Hopper defeated him in battle, Tsurugi trades Tendou the Sasword Zecter for cash, and Gon gives Tendou the Drake Grip.
Tendou joins ZECT in order to get all the Zecters and preventing Hiyori from being destroyed and destroy ZECT from within. However, Kagami disagrees and says Riders are there to fight Worms and protect humans. They fight and Gatack loses. Tendou gains the Hyper Zecter after Renge steals it for him. Mishima had the suitcase set up to destroy any evidence, and detonates the suitcase while it is in Uca Worm's hands. The Hyper Zecter reverses the flow of time and appears to Tendou. Through the use of Hyper Clock Up, Tendou saves Kagami from the Cammarus Worm. A Native called Tachikawa Daigo tells Tendou to stop collecting the Zecters. Tendou guards Tachigawa, as he knows Hiyori's whereabouts. Riku Kagami explains to him that the Zecters will drive them insane if they refuse to fight Worms. After Kabuto saves Daigo from the Worms, he experiences the 'berserk switch', almost killing Daigo in the process. The Hopper Riders arrive on scene and defeat them instead.
Tachigawa tells Tendou to 'find the solar eclipse' and dies because of Cochlea Worm. He then decided to release all the Zecters. Later on, Utilizing the power of all 4 Zecters, he defeated Lepotophyes Worm, but was taken through an involuntary Hyper Clock Up to a place 'devoid of all time' with the solar eclipse. After seeing Hiyori with another man, he is pulled back into his dimension. Tendou is then left wondering why he still can't control Hyper Clock Up. Rena challenges Tendou once more in hopes of taking the Hyper Zecter, but her memory gets erased due to Tendou's Hyper Sting attack. Drake and Kabuto end up fighting each other because Daisuke doesn't believe that Rena is still evil. Tendou picks Rena's Shibuya Meteorite fragment and is taken to Hiyori's dimension again. After confronting his Worm counterpart, Dark Kabuto, their Rider Kick collision forces Kabuto back to the real world. Tendou meets Reiji Nogi, and Nogi activates Freeze, defeating the power of Hyper Clock Up, forcing Tendou back into Rider form. During their second battle, Tendou learns from his mistakes and anticipates Nogi's use of Freeze. His Hyper Shooting stuns Nogi temporarily.
Tendou is then able to use the Perfect Zecter's Maximum Hyper Cyclone to defeat Cassis Worm Dimidius, only to have him evolve into a stronger form, Cassis Worm Gladius. Tendou wants to lose to Dark Kabuto so that he may discover Hiyori's location. However, after realizing this plan made him seem like a coward, his fighting spirit returns and he defeats Dark Kabuto, only to be interrupted by Hiyori who transforms into Sisrya Worm. She states that she is fine with living in another dimension and defends Dark Kabuto. After Hiyori leaves, Tendou tells to Kagami that the only way for her to be happy is to let her live with the fake Kabuto. Renge arrives, saying that the other world's entrance is opened when the solar eclipse occurs. Hiyori doesn't want to hurt Tendou anymore and tries to convince herself that she doesn't want to come back. Tendou, moved by this, leaves and goes after Hiyori as a solar eclipse starts. After chasing Hiyori back to her dimension, she realizes the one who really cares about her is Tendou, she leaves Dark Kabuto and returns to the human world. After discovering that Hiyori has been injured, he takes her to hospital, but she hides the fact that Dark Kabuto was the one that injured her. Tendou, along with Riku and Mishima, meet with Negishi, leader of the Natives. Tendou attempts to recruit other Riders in an effort to fight the Worms, but when he appears before Kageyama and Yaguruma, he finds them attempting to regain their darkness and quickly leaves. Tendou meets Nogi once again, as Cassis Worm Clipeus, but Nogi runs away soon after. After conversing with Kagami and Misaki, Tendou learns Tsurugi is a Worm and automatically decides to defeat him. Kagami says there is still good in him.
While Kagami leaves to fight Clipeus, Tendou goes and meets Jiiya, learning of a promise that he must fulfill. Tendou meets Tsurugi after talking with Jiiya and agrees to trade all the Zecters in exchange for Kagami's life. At the last moment, the Zecters are escape, and Tendou fights Scorpio Worm. Preparing for the final blow using the Perfect Zecter, Tsurugi suddenly appears from Scorpio Worm telling Tendou to fulfill his promise. Understanding that Tsurugi wants to destroy all Worms, Tendou slashes through Scorpio Worm's body. ZECT begins handing out Worm identification necklaces that alert the wearer of nearby Worms. Upon learning this, Tendou begins destroying the necklaces because they will turn them into Natives. By destroying the necklaces, the public begins to fear and hate Kabuto. Kabuto is able to defeat Dark Kabuto by using Hyper Clock Up along with the Maximum Hyper Typhoon. Gatack tries to persuade Kabuto to stop, but Kabuto continues destroying the necklaces until a blocked bullet from Tadakoro's gun goes stray and hits Renge. Kabuto then fires at Gatack and escapes the area, leaving an infuriated Tadakoro to care for an injured Renge. Tendou ends up rescuing Dark Kabuto from the clutches of Mishima and Negishi, who have taken over ZECT.
Not believing the truth of the necklaces, Gatack attacks Kabuto and defeats him with the help of the ZECT Troopers. Tendou recalls his words to Hiyori of him always being by her side. As he reaches for a lone flower, the rubble from atop him falls and crushes him. Tendou uses the flower to destroy the controls, causing the meteorite that was turning humans into Natives to overload. Then Hyper Kabuto defeats Mishima/Gryllus Worm together with Gatack, escaping the first explosion as an irritated Negishi was intend to make Tendou pay for ruining everything he sought to obtain. Dark Kabuto then rushes out at the last moment, telling Tendou to protect their world as he drags Negishi back into the explosion that killed them both. Realizing the battle is over, Tendou releases the Kabuto Zecter, and the Zecters fly away. Tendou and Kagami make up. During the epilogue, Tendou is shown in Paris improving his cooking skills.