Gojira: Kaijû Wakusei

In a distant future, 20,000 years after Godzilla took over, a young man named Haruo Sakaki (Mamoru Miyano) seeks revenge against the monster that killed his parents. He leads a group of human refugees, including Haruo's grandfather, to the exoplanet Tau-e, only to find it uninhabitable. After a series of events, Haruo discovers Godzilla's weak point and leads a team to kill the monster, but not before it is revealed that the battle has only scratched the surface, as a larger, original Godzilla emerges from beneath the earth.