Best known for his role of Dr. Who in King Kong Escapes (1967) and Dr. "Death" Shinigami in the Kamen Rider TV series, Hideyo Amamoto was initially setting himself up for a job in politics. This was after a rough patch in World War II, from which Amamoto was drafted into and received several sanctions from rebelling against superiors. After the war, in 1948, he attended the Tokyo Imperial University's Law Faculty under their political department. He dreamed of being a diplomat, but was dissatisfied with current political attitudes in the country. Disillusioned, Amamoto dropped out of University to pursue a career in the arts instead.

Amamoto started out his acting career with the Hayuza group. He landed his first theater performance at age 28 in 1954. He was noticed by Toho due to his "unusual size and appearance" alongside his acting skills. The firm then hired him to work in their films, signing the actor to an exclusive contract in 1958.

Working for Toho, under the stage name Eisei Amamoto for most of his career, the actor started out playing several small parts in the late 1950's and early 1960's. He was typically cast in villainous roles, most often as a henchman for a film's main villain. He rarely took center stage in a movie, although turned heads when he took the main role as Dr. Who in King Kong Escapes (1967). The was followed up by a role as Shinpei Inami, a Toy Maker, in All Monsters Attack (1969), playing a fatherly figure to a small boy which was well outside of his normal typecast roles. Amamoto eventually garnished a cult following in Japan, due to his performances in Toho movies and other Japanese television shows such as Kamen Rider.

Director Shusuke Kaneko would give Amamoto his last role in the film Godzilla, Mothra & King Ghidorah: Giant Monsters All Out Attack (2001) as the Prophet Isayama. Kaneko wrote the part in the film especially for Amamoto.

Other names: Eisei Amamoto (あまもと えいせい)