|This article is about a/an evil organization in Kamen Rider Wizard and Kamen Rider Fourze.|
The Monster League (怪人同盟 Kaijin Dōmei) is a club composed of psychic students who wish to create a new Earth with a superior breed of humans. The Monster Alliance appears in Kamen Rider × Kamen Rider Wizard & Fourze: Movie War Ultimatum. The Monster League is a homage to the Youth League from Inazuman, which was created by Shotaro Ishinomori. Actually, 5 years ago, (during the main timeline), the members of the Monster League are actually a group of children (which turn out to be Gates) whose mind were used by Akumaizer Xatan himself in order to achieve his evil plan. However, Fourze (who came 5 years from the future) and Wizard came just in time to save them. After Gentaro's return from the past, Saburo renamed the group as the Shounen League acting as a support group for Miyoppe's Space Kamen Rider Club.
- Main article: Saburo Kazeta
Saburo Kazeta (風田 三郎 Kazeta Saburō) is a psychic young man who is the leader of the Monster League and can become an armored larva-like mutant known as Sanagiman (サナギマン) by shouting "Gōriki Shōrai" (剛力招来 "Summon Mighty Power"). As Sanagiman he is extremely durable against any attack and has superhuman strength. Saburo is supported by a mysterious figure known as Kageto Banba who gives him a device called the Zeber (ゼーバー Zēbā), which enhances psychic powers. He is also able to become a more powerful blue moth-like mutant known as Inazuman (イナズマン) by shouting "Chōriki Shōrai" (超力招来 "Summon Super Power").
Saburo is a homage to Inazuman as he appeared in the original manga, based on the hero's human identity as Saburo Kazeta (風田 サブロウ Kazeta Saburo). While Inazuman's design is based on the manga, the Zeber is a homage to the device that the TV version of Inazuman uses in Inazuman Flash.
Saburo Kazeta is portrayed by Kenta Suga (須賀 健太 Suga Kenta).
- Main article: Rumi Komaki
Rumi Komaki (小牧 瑠美 Komaki Rumi) is a female member of the Monster League and is nicknamed "Ruby" (ルビー Rubī).
Rumi Komaki is portrayed by Kasumi Yamaya (山谷 花純 Yamaya Kasumi).
- Main article: Daita Kondou
Daita Kondou (近藤 大太 Kondō Daita) is a member of the Monster League and is nicknamed "Kong" (コング Kongu) due to his overweight body.
Daita Kondou is portrayed by Kazuyoshi Nagazawa (中澤 兼利 Nagazawa Kazuyoshi).
- Main article: Chikao Nezu
Chikao Nezu (根津 誓夫 Nezu Chikao) is a member of the Monster League and is nicknamed "Nezumi" (ネズミ) due his surname, which means "rat" or "mouse" in Japanese.
Chikao Nezu is portrayed by Yuya Hara (原 勇弥 Hara Yūya).
- Main article: Kageto Banba
Kageto Banba (番場 影人 Banba Kageto) is a mysterious man who supports the Monster League and created the Zeber in a deal with the Akumaizers. Kageto is also one of Gamou's comrade but however, he left Gamou to study on psychics. He uses an Zodiarts Switch to become the Hercules Zodiarts (ヘラクレス・ゾディアーツ Herakuresu Zodiatsu) which has immense physical strength and the power to summon Dustards.
Kageto Banba is a homage to Emperor Banba, the main antagonist of Inazuman.
Kamgehito Banba is portrayed by Toshiya Toyama (遠山 俊也 Toyama Toshiya).