When an op goes wrong and FBI agent Zack's partner dies, his search for the one responsible takes him to a yakuza in Japan. A mob boss wants revenge for his son's death and Zack's his target.

A large monster attacks Japan, but dies suddenly. While the people rejoice and bask in relief, the giant corpse left behind begins to slowly rot and bloat. If it explodes, the nation will be destroyed.

As the threat of giant unidentified lifeforms known as "S-Class Species" worsens in Japan, a silver giant appears from beyond Earth's atmosphere.