Nana Toshi Monogatari

A catastrophic event alters Earth's axis, placing the poles along the equator and resulting in the death of all life on the planet. A lunar colony, unaffected by the disaster, initiates a plan to repopulate Earth by building seven cities in key locations. To maintain control, the moon enforces an orbital defense system that prevents any flight above 500 meters. When a virus wipes out the moon's population, those on Earth are left isolated. Political conflicts among the seven cities persist despite the new reality.