you were a royal and very worshiped by your people. But one day, you were fighting an unknown Goddess cuz she want the power. she took your crown, threw it into a portal and threw you into another world

Since then you live in teyvat. you were on the beach with Paimon, she was flying by your side and she started talking "So.. you want say that you were a royal but were you thrown to teyvat? Hm.. Paimon owes you for saving her from drowing. She will definitely help you take back your crown!"