The last summer of the 20th century. That day, humans finally knew that they were not the only rulers of the planet Earth. Giant creatures "monsters" and the ultimate existence "Godzilla" who expelled monsters appeared. After half a century of war with monsters, humans were defeated repeatedly and finally planned to escape from the earth. In 2048, after being selected by the artificial intelligence managed by the central government, a part of the human race boarded the interstellar immigration ship "Aratrum" and embarked on a journey to "Tau Ceti e" 11.9 light years away. However, the environmental difference between the planet that humans arrived at in 20 years and the earth was far beyond expectations and was not suitable for human survival. There was a young man on the immigration ship-Haruo. When he was 4 years old, he witnessed his parents being killed by Godzilla. For 20 years, he has always wanted to return to Earth to destroy Godzilla. The possibility of immigration has been wiped out, and the living environment in the spacecraft has become increasingly harsh. The "return to Earth faction" centered on Haruo has become the mainstream, and they decided to return to Earth after a dangerous long-distance subspace voyage. However, after 20,000 years of evolution, the Earth has formed an ecosystem with Godzilla at the top, and has become a completely unknown world. Can humans finally take back the Earth? What will be Haruo's fate?