Kaishoku Rinne

Long ago, an obscene ritual took place...

The town Onorochou was well known for their flourishing fishing industry. But that industry had recently started to crumble, because of a sudden steep decrease in catches.
The people of Onorochou were at a loss. What were they to do, if the low catches continued?
It was then someone from the town decided to commence an old ritual.
It was said that this ancient ritual would guarantee the town bountiful catches.

In order to do this ritual, however, a set of chosen shrine maidens had to step into the forbidden part of the town... an area which had been locked away for ages.

There, the chosen shrine maidens would have to surrender their bodies to the creatures of the sea for 7 days straight.

What fate awaited the chosen shrine maidens, Amami Kiyoka and Shigano Koko?

[Translated from the official summary]