Takato's younger sister Utako has always been a frail child – constantly shut up inside the house and not even allowed to venture outside into the sun. But she's cheerful and affectionate, and Takato can't bring himself to be dissatisfied with the situation at home.

But when he returns to his village after a semester away at his new boarding school, Takato begins to notice changes, not just in Utako but also in his two childhood friends, who seem to know more than they're letting on. And what does all this have to do with an old but infamous folk tale in the village?