As the theme song denotes, no one knows who Gekko Kamen is. He is a lone figure dressed entirely in white, who mysteriously appears when danger is afoot.
 
While he appears to be a regular human, he is exceptionally gifted in many areas including unarmed combat and gymnastics. He is an expert motorcycle rider and a superb marksman. (Source: AniDB)

Shounen Club version. 
Manga adaptation of the TV show.

Book rental version. 
Manga adaptation of the TV show. From 1958 to 1959, all seven chapters were published by Suzuki Publishing. Kyuji Inoue is in the 1st to 4th chapter (first arc), and Kazuo Murayama is in the 5th to 7th chapter (second arc).

Gekkou Kamen is retired on the moon, so his trusty motorbike returns to Earth to find a new hero to take over the job of defending the Earth from alien invaders.

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