Kenji Sahara as Dr. Yuzo Mamiya

Kumi Mizuno as Akemi Togawa

Russ Tamblyn as Dr. Paul Stewart

Jun Tazaki as General Hashimoto

Kipp Hamilton as Singer

Yoshibumi Tajima as Officer Hirai

Nobuo Nakamura as Professor Kita

Hisaya Itō as Chief Izumida

Nadao Kirino as Lt. Col. Kazama

Ren Yamamoto as Saburo Kameda

Kōzō Nomura as General's Aide

Shōichi Hirose as Soldier

Tadashi Okabe as Defiant Reporter

Hideo Shibuya as Skeptical Reporter

Ikio Sawamura as Fisherman #1

Seishirō Kuno as Fisherman #2

Someshō Matsumoto as Official

Gorō Mutsumi as Dr. Paul Stewart (voice)

Haruo Nakajima as Gaira

Hiroshi Sekita as Sanda

Yasuhiro Komiya as Adolescent Sanda

Kasei Kinoshita as Adolescent Sanda (voice)

Yū Fujiki as (uncredited)