Chase (チェイス Cheisu) is a specially created Roidmude who was originally Krim Steinbelt's aide Roidmude 000, dubbed Proto Zero (プロトゼロ Puroto Zero), who copied the appearance of the traffic police officer Koichi Kano (狩野 洸一 Kano Kōichi). During the Global Freeze, Proto Zero attempted to fight off the rampaging Roidmudes as Kamen Rider Proto Drive (仮面ライダープロトドライブ Kamen Raidā Puroto Doraibu), before being captured and reprogrammed by Freeze, Heart, and Brain to work for them. His memory has been altered with no recollection of his past, and is referred by the Roimudes as the "Grim Reaper" (死神 Shinigami) and is tasked to hunt down out-of-line Roidmudes and destroy their physical forms while taking their numbers to be reformatted by Brain. He is soft-spoken and sees Drive as his rival. In battle, he transforms into a Kamen Rider-like form called Mashin Chaser (魔進チェイサー Mashin Cheisā),[c] and is armed with the Break Gunner (ブレイクガンナー Bureiku Gannā) fire arm and drives the Ride Chaser (ライドチェイサー Raido Cheisā) motorcycle. He later receives Chaser Viral Cores (チェイサーバイラルコア Cheisā Bairaru Koa) which allows Mashin Chaser to become the armed Tune Chaser (武装チェイサー Busō Cheisā) forms, which each have their own weapons. Some of his memories of his former life arise when he sees Kiriko Shijima, who he once saved as Proto Drive, so he continues to meet with Kamen Rider Drive in order to discover his previous identity. Despite Medic's attempts to keep him from remembering his past by changing his purpose to serve as the Roidmudes' defender, Chase fully regains his memories when Kiriko tends to his wounds after a fight with Kamen Rider Drive. Using a Mach Driver Honoh and the Signal Chaser (シグナルチェイサー Shigunaru Cheisā) Signal Bike, reverse engineered by Rinna Sawagami from Mashin Chaser's armor, to become Kamen Rider Chaser (仮面ライダーチェイサー Kamen Raidā Cheisā), armed with the Shingou-Ax (シンゴウアックス Shingō Akkusu, Signal Ax), while still using the Break Gunner as a firearm. He also later receives the go-kart-like Ride Booster Blue (ライドブースターブルー Raido Būsutā Burū). When the Shift Prototype Car is repaired, Chase uses it in his Break Gunner to retrieve all his memories, revealing to everyone that Freeze, Heart, and Brain were responsible for his reprogramming, and also revealing Soichi Makage's true identity as Freeze. When Tenjuro Banno returns, Chase is skeptical of his creator's intentions and witnesses Banno's betrayal. After Chase learns the concept of human emotions, he now has a dream to become one like them, in following their good example. Chase also realizes that he loves Kiriko but discovers that Shinnosuke does as well. He reveals his love of Kiriko to Go, who refuses his humanity and reminds Chase that Kiriko cannot love a "machine". When Kiriko is hospitalized, Chase asks if she loves Shinnosuke, which she tries to deny but Chase sees through her ruse. Chase leaves, shedding tears upon realizing that Kiriko does not feel the same for him, willingly holding the burden of his unrequited love as it makes him feel closer to being human. During the final battle against Banno, Chase's Mach Driver Honoh is destroyed. Gord Drive takes Chase's Shingou-Ax to kill Go, but Chase transforms into Mashin Chaser one last time to save Go. He is mortally wounded by Gord Drive's attack, and as he is about to die, Chase tells Go of his dream to protect something important and wanting to become human. He leaves the Signal Chaser and his driver's licence to Go and charges at Gord Drive, activating his self-destruct mechanism. Go watches in horror as the explosion engulfs them both and Chase's Core is destroyed, after which he uses the Signal Chaser to fight Gord Drive as Kamen Rider Chaser Mach and destroy Banno's Drive Driver with the Shingou-Ax. After the world is saved, Go takes the Signal Chaser with him to America in the hopes that Harley Hendrickson can use it to bring Chase back to life. Elsewhere, Shinnosuke and Kiriko happen across Koichi Kano.
During the events of the film Kamen Rider × Kamen Rider Ghost & Drive: Super Movie War Genesis, Chase, along with all Roidmudes, has been brought back to life due to Takeru Tenkūji altering the events of the past in hopes of making sure his father lives. This is all part of the Da Vinci Gamma's plot to change the future to his liking. Chase, however, still possesses his memories of the original timeline and is not focused on attacking humans and he assists the Kamen Riders once more. After the Da Vinci, Raphael, and Michelangelo Gammas are defeated, history is restored back to normal, and the Roidmudes all disappear once more. However, Chase bids Go Shijima one final farewell before he disappears.
In novel and movie saga of Kamen Rider Mach, Chase's human sync, Koichi joins the Special Investigation Division. In final battle between Kamen Rider Mach and Revenger/005 Roidmude, it is revealed that Chase's core is actually being revived within the Shift Ride Crosser Shift Car and possessed his human sync for temporary before he fades away from Koichi's body, as well as the one who gave Go Shift Ride Crosser for Go's use to transform into Kamen Rider Mach Chaser and helps him to clear Reiko Nishimori's name from being framed by that Roidmude.
Chase is portrayed by Taiko Katono (上遠野 太洸 Katōno Taikō), who also portrays the real Koichi Kano. In Drive Saga, his early days as Proto-Zero is voiced by Daichi Endō (遠藤 大智 Endō Daichi).