Sorayume

Morinaga Satsuki is the only daughter of a family that owns an antique store, with no special redeeming features she is a extremely normal 2nd year high school student. It's the 24th of August, with one week left in her summer vacation. On the day that her parents leave for a purported business trip she spontaneously by chance finds a sparkling yellow ring, "Chrysoberyl".

When Satsuki took that ring and put it on, the man sealed inside was summoned into this world.

He called himself a demon called "Ruen Egrandin".

He semi-forcefully asked her to help him find the "Thing he was looking for", and as a reward he would grant her a "wish that wasn't particularly a wish".