In the aftermath of World War II, a scientist in post-war Germany conducts experiments using the heart of Frankenstein. When the heart is irradiated by a nuclear blast, it grows into a giant monster. The creature, known as Frankenstein's Monster, goes on a rampage in Japan, destroying everything in its path. It is up to a team of scientists and military personnel to stop the monster before it destroys humanity.

In The War of the Gargantuas, two giant monsters, one brown and one green, emerge from the sea and begin wreaking havoc. As they clash with each other, the city is left in ruins and humanity is in danger. It is up to a team of scientists and the military to find a way to stop these gargantuas before it's too late.