[4][page needed] The film starred Peter Dyneley as a foreign correspondent in Japan who is given an experimental drug which causes an eye and eventually, a second head to grow from his shoulder.

[5] American foreign news correspondent Larry Stanford has spent time in Tokyo, Japan and explains to his boss and friend Ian that he looks forward to going home to his wife Linda and the US.

The doctor has discovered that human evolutionary alterations may be naturally caused by sporadic atmospheric conditions, but change by chemical means is also possible.

In response to Larry's inquiries, Suzuki amiably steers the conversation to asking some personal questions such as age and health status, upon which the doctor decides this man is qualified to be a test subject.

Ian finds the incriminating prayer bracelet and takes it to police, who are also concerned about an unusual rash of street murders.

[3] Shinpei Takagi handled the special effects,[8] George Wyman played the titular monster and Hirooki Ogawa composed the soundtrack.

[9] Lopert Pictures released The Manster in the United States on March 28, 1962 as a double feature with Eyes Without a Face.

[11] The review criticized the fact that the second head of the character appears to only "bob up and down on the actor's raincoated shoulder, only visible in night scenes and never in close-up".

[11] In a retrospective review, AllMovie film critic Hal Erickson wrote, "Manster is a favorite among campy horror aficionados and for good reason as it is both unintentionally funny and genuinely creepy...Wait till you see the climax, with the hero battling himself on the edge of a live volcano".