A world existing on one of the branches of possibility.

There, artificial magic circuit devices called Artifacts were created,and the miracle known as magic became accessible to everyone.

In order to control that immense power, the people established the Artifact management organization Sephiroth,and under its management, research on Artifacts continued to be conducted day by day.

Then, new arrivals appeared at Sephiroth.

A girl who manifested magic far too powerful for her body to contain, and a young man assigned as a researcher to treat that girl.

The promise the two swore becomes a possibility,and extends a new branch in this world.