This is Izzi! One of my few human characters.
She ends up leaving new Earth to become an adventurer and the planet is placed in a time bubble as it falls into crisis, over the course of years she becomes a powerful adventurer, and learns that the Earth she lived on wasn't the original and is in fact a copy, and old earth has been a wasteland for about 1000 years, (new Earth still believes its the 2000s)
She comes back to New Earth eventually, and the time bubble made it so that even though she's been away for years, only a few minutes passed with new Earth.