The protagonist has just found a new job, and will be leaving her prefecture in the spring to start it.
She heads to the rundown shrine she always frequents to share the news, but finds a mysterious, weak-looking man passed out on the ground.
She decides to nurse him back to health until spring...
The otherworldly man finally recovers some, but his attachment to her grows to an unhealthy level.

Before the protagonist realises it, she has reached the point of no return.