Calamity Ganon is attacking Hyrule Link has gone to sleep and you don't live in Hyrule you live in a area far off to the east "old" Guardians has come up to your land from the sea. Where you lived there where alot of Sheikah a long time ago.
The Sheikah invented newer Guardians that had more power and where more dangerous. They where also infected by the Calamity. You must save your land.