Apocalypse in the Multiverse

There is a war against giants and others and all major continents are destroyed by war. Five girls on horses bring about the apocalypse. After the apocalypse the five horse girls leave through a portal to another Earth. On another Earth civil wars break out in the 1920s, the ancestors of Akiyo. Before Akiyo's birth there is an all out nuclear war with nuclear winter and nuclear summers caused by a green, and a blue alien. Akiyo is born in a bunker, on the day that she is born a cave system opens up for cave trials, the door is locked until her 5th birthday. She later goes through a portal into another Earth at three hundred million years before present.