Rikiya Tomizono as Sabimaru Tsuruhara, a brainy alchemist and one of Rinne's classmate. He is extremely misanthropic, and carries a tablet with a built-in AI named "Isaac" who talks for him. Just like Hotaro, he likes Chemy.
Amon Kabe (Good Life - Arigatou, Papa. Sayonara) as Ryo Kajiki, Hotaro's classmate and a boy who loves the occult. He is an avid reader of the Paranormal Planet magazine.
Kanji Ishimaru (Time Traveller) as Fuga Kudo, Rinne's father who was an outstanding alchemist, and was protecting the Chemy from the Three Dark Sisters, but when he was cornered, he entrusted Hotaro with the Gotchardriver.
- Alisa Sakamaki as Lachesis, the youngest daughter who uses a special alchemy that is activated with the tone of her voice.
- Itono Okita as Atropos, who looks like a young girl, but she is the eldest sister. She can use powerful alchemy.
- Kanon Miyahara (Kamen Rider Amazons) as Clotho, the middle child who is good at fighting.
High school student Hotaro Ichinose is entrusted with the Gotchardriver and is given the mission to collect all the Chemy that were released in this world. That said, if a Chemy is a reassuring human companion when it resonates with someone with a good heart. This is the case with Hotaro who loads the Hopper1 and Steamliner Ride Chemy Cards in the Gotcha Driver to become Kamen Rider Gotchard SteamHopper! But if a Chemy will combine with a human filled with malice, there is a danger in creating a creature known as "Kaijin Malgam". Will Hotaro "Gotcha" all 101 Chemies? What kind of strange combinations will form along the way once Gotchard gets more Ride Chemy Cards? What is in store for the alchemist Rider who manipulates cards?
TV-Asahi's Takehiro Okawa will serve as the show's general producer with TV-Asahi's Takehiro Okawa (Ohsama Sentai King-Ohger) and Toei's Yosuke Minato (Ohsama Sentai King-Ohger) will produce the series. The series will be written by Keiichi Hasegawa (Ultraman Nexus, Kamen Rider Saber, Gridman franchise) and Hiroki Uchida (Kamen Rider Jeanne & Kamen Rider Aguilera with Girls Remix). Veteran Super Sentai action director and suit actor Hirofumi Fukuzawa will serve as the show's action director, with Ryuta Tasaki (Kamen Rider Build) serving as the show's main director. Hiroshi Takaki (Samurai Sentai Shinkenger) will compose the show's music. Lastly, BACK-ON will perform the show's theme song, "CHEMYxSTORY".
Kamen Rider Gotchard is set to premiere this September 3rd only on TV-Asahi's Super Hero Time block, replacing Kamen Rider Geats.