From the introduction:
The land of the Elemental Nations is well known and covered in the Naruto, Naruto Shippuden and Boruto anime, manga and movies. This is not covering either of those times. Welcome to the world before the Elemental Nations truly formed, in the age when Kaguya first ate the Chakra Fruit of this land. You will be staying here through the rule of the Rabbit Goddess, the birth of her sons, Hamura and Hagoromo, those two sons rebellion against her tyranny, the birth of the juubi, then the bijuu and the birth, growing up, and falling out of the Sage Hagoromo’s two sons, Indra and Asura, which then blossomed into the greatest blood feud the world ever knew, between the Senju and the Uchiha, Overall, you’ll spend about 100 years here, during which time you will not die of old age. This jump starts when Kaguya arrives in this dimension, then would normally end when Indra and Asura would have had their final battle.