She and I Were on the Mountain at the End of the World

This is a world where the earth has been invaded by unknown objects, and human beings in various countries have almost suffered catastrophe and are about to be destroyed. The surviving countries that are barely hanging on are huddled in the shrinking living space. In order to continue the human race, the remaining countries united and established places to cultivate specialized forces. Modern weapons called mechas came into being, but they still could not stop the invaders. In times of crisis, who stands up to save the future of mankind? And what kind of love and hatred will he or she weave? She and I were on the mountain at the end of the world...