Luminous Majin Island

A boy, Saburo Yamagata, and his older brother, Takeshi, discover a dying man on the beach. The man dies, leaving behind the words ``Night-Light Island,'' and Saburo takes
a photo of a stingray-like monster that appears in the sky. Later, when Saburo and his friends try to develop the film at home, they are attacked by a stingray and the film is taken away. Saburo and Takeshi head to the beach where the stingray first appeared
in order to find out what it is, but the stingray attacks again and takes them to Yokojima Island...!?