Nana Toshi Monogatari: Hokkyokukai Sensen  

A Tale of Seven Cities - the Arctic Front, Seven Cities Story: Arctic Front, 七都市物語 ~北極海戦線~, 七都市物語 ～北極海戦線～

In 2099, Earth's rotation shifted off its axis by 90%, causing natural disasters for three years. The aftermath left only two million moon colonists remaining, and they returned to begin repopulating seven new cities on Earth. However, the remaining lunar colonists were fearful of their former neighbors and constructed a ring of defensive satellites around the newly populated homeworld to prevent any potential threats from arising again.