A quiet, moonless night.

Tsukishiro Michiru has a dream of being lost inside a mysterious old castle. She meets with five jewels that had taken the form of attractive men.

She is ordered by the castle's master. "Choose the jewel you think suits you the best by the night of the next full moon"

However, the jewels only have exceedingly harsh personalities that would be called "cruel", "beastly", "sadistic", "scheming", or "yandere"!

As though being guided by something, in the real world she then meets five men that look the same as the jewels she met in the dream world.