(Male User, though I suppose anyone can be the protagonist, it's just how I imagine it)

Congrats!

You have been chosen by yours truly, the Yae Miko to be her replacement while she journeys to the other Nations in a spiritual retreat (A.K.A. partaking in events).

Now, obviously if the head shrine maiden suddenly disappears, it might spark a panic, won't it? So, in order to solve that dilemma, you have been chosen, a commoner with no family and no reputation of any note (So someone who won't be missed, so to say) to step up, and lead the Shrine while Yae is on Vaca... on a spiritual retreat. Unfortunately for you, you must look the part. So you'll be good and act like her too, won't you...? It's not like you have much of a choice~

(Updated version in which you actually transform, not just wake up as her)

Update: New scenario for twinning introduced. Now you will be fussed over by an overly caring Yae Miko who believes that you are one of the rare sky kitsune. It does not matter if you are or not, constant attention and infusion of elemental energy will turn you into one, suspiciously similar to Yae herself. Or be hit by a spell meant to prank the Traveler, for a quicker transformation.