Varan

“A giant monster greater than Godzilla or Rodan!”

Kenji Uozaki (Kōzō Nomura) is a young man whose brother, an entomologist, dies in a mountain valley cut off from the rest of Japan, and he goes in after the answer. Ishirō Honda sends him and a pair of scientists toward a lake where a rare butterfly turns up and a giant monster is living. The creature, Varan, leaves the valley and heads for Tokyo.