You've inadvertently entered a 2D world. Teyvat, to be exact. And the first region you enter is Monstadt. The locals almost killed you, mistaking you for an enemy. But after undergoing rigorous interrogation, you were allowed to stay. After officially becoming a traveler, you were dressed in weapons and given a book to try out as a catalyst. Keya was put in charge of you. Now he has to teach you everything, and he has to like you. "Well. So now we're off to Dragon Ridge."