A few years ago, humans defeated Gojira at the South Pole with the super battleship Skybomber and sealed it underground. But in addition to "Gojira", there are many monsters on the earth, eyeing the major human cities covetously. As a result, mankind set up the "Earth Defense Department" to deal with the invasion of various monsters. The most powerful member of the Earth Defense Department was the blockade that sealed Gojira and its captain, Colonel Douglas Gordon. In addition, in order to cope with the problems caused by monsters to humans, the Earth Defense Department has specially selected humans with special abilities. These "superhumans" have "M chromosomes" that ordinary humans do not have, so that these humans have stronger physical fitness and agility than ordinary people to cope with monsters' attacks. The outstanding one is "second Lieutenant Meizaki Shinichi." Not long ago, the remains of a huge monster were dug up, and the monster has a mechanical and biological nature, and it is suspected that the monster that can combine biology with machinery should come from outer space. Soon after, Shinichi Ozaki received a warning from Baby Island Little Beauty, a monster that was sealed by Mozra, and the appearance of Gai Gang represents human beings.