The Earth has suffered from terrible wars, and the United Nations' World Federation Government was formed as a result. 33 years later ULF (United LUNA Front) has emerged and declared inter-planetary war to UNWF. The Moon gains initiative and transfers battlefield to the Earth.

In the meantime, there is a group of self-described pirates "E-Freeze" in the sea near Antarctica. They have technical skills comparable to "ULF" and ability to fight in any environment with their humanoid all-purpose weapon GrastX. Main character starts as a member of these pirates.

[From vndbreview]