Go Shijima (詩島 剛 Shijima Gō) is Kiriko's younger brother. He has been living in the United States for some time as a freelance photographer, but has returned to Japan where he reveals he is another Kamen Rider, Kamen Rider Mach (仮面ライダーマッハ Kamen Raidā Mahha). Go hates all Roidmudes because he has discovered that his father is Professor Banno and he wants to wipe out all of his father's creations. He holds a particular hatred towards Chase, even after Chase regains his humanity, but he soon mellows out and accepts Chase as another heroic Kamen Rider. When Go discovers that his father's consciousness has been stored in a tablet computer used by Brain, he goes on an undercover mission, pretending to betray Kamen Riders Drive and Chaser to get closer to Brain and Freeze. He still supports them, having used the alias "Mr. X" to contact the Special Investigations Division during his secret mission. When he has the opportunity, he steals the tablet from Brain, blowing his cover to save his father. He tries to convince Mr. Belt to work alongside Banno so they can both wipe out all of the Roidmudes, but Mr. Belt angrily declines due to their past, all while Go reveals that he knows Banno is his father, inadvertently revealing the truth to Kiriko as well. Go is shocked when Banno reveals he has been using him to enact his own plans to cause the second Global Freeze. Betrayed, Go and Chase hunt down Banno, who has taken the form of Gord Drive. Chase falls in battle, giving Go the inner strength to defeat his father. He uses Chase's Shingou-Ax to completely destroy Gord Drive's Drive Driver, finally freeing the world from his father's evil. After the Special Investigations Division is disbanded, Go departs for America with Professor Harley Henderickson, hoping to use Chase's Signal Bike to bring him back. Go later becomes a famous photographer.
In a novel adaption of his storyline Mach Saga, explains how he held a grudge against the Roidmudes was because some Roidmude named Gunman had killed Go's friend, Ethan Woodward (イーサン・ウッドワード Īsan Uddowādo), and Go was too weak against his friend's murderer, until Harley rescues him to prepare Go to fight Roidmudes' threat as Mach before he returned to his home country, Japan. When most of the former Neo-Viral Core user criminals whom Special Investigation Division arrested, Go visits one former Neo-Viral Core user criminal, Koya Nishihori's daughter, Reiko and both shares their feelings towards each other, such as sharing their similar past backgrounds. He is unable to save Nishihori from using Anima System into maximum voltage, which kills his mind and leave only his corpse. In the same time Reiko got poisoned and manage gives Go the hints from the death of Ethan and Chase, Shinnosuke's near-death experience and Banno's reawakening when Go manage to take her to hospital in time. Once he got the evidence, and obtain both prototype of Mach Driver Honoo and a new Shift Viral Core from Rinna, Mach confronts the true culprit, who is none other than Roidmude 005, whom Kamen Rider supposedly destroyed, but recently his the core recovered and reviving his body, thus transformed to Revenger Roidmude. As Go transforms into Chaser Mach to fight, but he is overwhelmed by Revenger's strength being above of Gord Drive. At the end of the 5th minute, Go lands a punch on Revenger before the transformation is cancelled, then later uses Shift Viral Core to transform into Super Deadheat Mach, and presumably destroys Revenger with a Rider Kick. By the time during Mach Saga's movie, he soon learned that Reiko is framed for the crime she never committed, leading Go to defend her and find a proof that she's innocent, thus finding a true culprit who framed Reiko, and is none other than the still alive late-Nishihori's Roidmude sync Revenger. With the help of Chase-possessed human sync, Koichi Kano, Go is being given a Shift Ride Booster Car to transform into Kamen Rider Mach Chaser and destroys Revenger permanently, thus clearing Reiko's name as both Go and Reiko starts dating.
To transform into Kamen Rider Mach, Go uses the Mach Driver Honoh (マッハドライバー炎 Mahha Doraibā Honō) belt and one of many Signal Bikes (シグナルバイク Shigunaru Baiku) for either transforming or initiating a Signal Exchange (シグナル交換 Shigunaru Kōkan). It uses an updated version of Drive's technology called the Next System (ネクストシステム Nekusuto Shisutemu) which is apparently more powerful. Mach can also use Drive's Shift Cars for Tire Exchanges, but Drive cannot use a Signal Bike as the Drive Driver does not have the Next System. Using the Shift Dead Heat Shift Car, Mach can become the powered-up Kamen Rider Deadheat Mach (仮面ライダーデッドヒートマッハ Kamen Raidā Deddo Hīto Mahha) form. He drives a motorcycle known as the Ride Macher (ライドマッハー Raido Mahhā) that can combine with Chase's Ride Chaser to form the car Ride Crosser (ライドクロッサー Raido Kurossā). He also later receives the go-kart-like Ride Booster Red (ライドブースターレッド Raido Būsutā Reddo). His primary sidearm is the Zenrin Shooter (ゼンリンシューター Zenrin Shūtā, Front Wheel Shooter), which can also perform Full Throttle finishing attacks. Using Chase's Signal Bike, Go can transform into Kamen Rider Chaser Mach (仮面ライダーチェイサーマッハ Kamen Raidā Cheisā Mahha), allowing him to use the Shingou-Ax as well as summon the three Viral Cores used by Mashin Chaser to fight by his side. In Type Lupin! ~Lupin, the Last Challenge~, it was revealed that the Mach Driver Honoh he used contained Krim's backup A.I., which he used to restore the Drive Driver when visiting the Drive Pit sometime in Movie War Full Throttle. In his novel storyline Mach Saga, he obtain a modified Chase's Rhino Super Viral Core called Shift Viral Core and a prototype Mach Driver Honoo from Rinna to transform into Super Deadheat Mach (超デッドヒートマッハ Chō Deddo Hīto Mahha) form, a form which is described to be a white version of Super Mashin Chaser with Mach's head and Chaser's orange eyes, yet also powerful than Chaser Mach form. During a final battle against Revenger Roidmude in Drive Saga: Kamen Rider Mach, Go obtain the Shift Ride Crosser Shift Car from presumably Chase (revealed to be a possessed Koichi Kano) to transform into a second variation of Chaser Mach known as Kamen Rider Mach Chaser (仮面ライダーマッハチェイサー Kamen Raidā Mahha Cheisā), in addition from the power of Ride Crosser.