- Gatack Zecter - Transformation device for Gatack
- Rider Belt - Transformation Belt for Gatack
- TheBee Zecter - Transformation device for TheBee
- Rider Brace - Transformation Brace for TheBee
- Hyper Zecter - Transformation device for Gatack to become Hyper Form.
- Gatack Vulcan - Gatack's personal weapons in Masked Form
- Gatack Double Calibur - Gatack's personal weapons in Rider Form
- Gatack Extender - Gatack's Rider Machine
- Souji Tendou: At first, he considered Souji as a weird person but later wanted to befriend with him. After his fail effort to become his friend, Arata marked him as his rival who he wants to surpass. In the end, he become the best friend for Souji.
- Yuzuki Misaki: Yuzuki is the most trusted ally on his team to make a move and working together to fight Worms secretly with their own way.
- Shuichi Tadokoro: Shuichi also the most trusted person on his team to save people from Worms' harm. There is one time he rejected Shuichi due his true identity as Native, but later he reconciled with him.
- Hiyori Kusakabe: At first, it is looked like Arata cares Hiyori as friend. But later revealed that he is in love with her (as a proof in Kabuto movie which is taken on pre-Alternate timeline), even still accepting her as Native. He and Souji keep the secret about her true identity.
- Jyuka Tendou: He befriend with Jyuka despite Souji's reluctant of having Jyuka as his friend. He also cares Jyuka like his own sister.
- Yumiko Takemiya: His boss at part time job. There are times she helps Arata to get closer to Hiyori.
- Daisuke Kazama: Arata marked him as weird as Souji. They have no close relationship as Arata only have a conversation with him for joining Zecter and help on certain incident.
- Tsurugi Kamishiro: He is the first Rider to befriend in unfortunate way. Arata cares so much about Tsurugi and tried to keep secret about himself as Scorpion Worm.
- Jiiya: Jiiya entrusts Arata about Tsurugi's forbidden secret and both always discuss about what to do with Tsurugi for times.
- Renge Takatori: At first, Arata and Renge had a very bad relationship. Arata dislike her childlish attitude while Renge dislike Arata for being a clumsy senior. But later, their relationship as formidable ally is made during the incident of Ghost at school when Arata tried to cheer up students when they were trapped in bus with mists which was Worm's attack
- Riku Kagami: Arata at first have a hatred with his own father because of his emotionless of the death of Ryo Kagami, his second son. But after learning more truth about what has Riku through, Arata finally have their relationship as family once more.
- Ryo Kagami: Arata cares so much of his young brother. After his death, Arata determined to hunt almost all Worms that existed
- Masato Mishima: Arata has a long dislike about Masato, especially after learning what kind of person exactly he is. During the final battle, Arata is so determined to finish him for good.
Kamen Rider X
Kamen Rider Amazon
Kamen Rider Super-1
Kamen Rider ZX
Kamen Rider Black/RX
Kamen Rider Kuuga