After performing a mysterious ritual for eternal life, twelve-year-old Yuna Tsukishiro awakens in another world inside the body of an orphaned girl.

In this world, supernatural beings known as otherworldly gain extraordinary powers through mysterious potions and ancient rituals. As Yuna searches for a way home, she discovers a hidden world filled with secrets, dangerous powers, and forgotten mysteries.

One night, another ritual transports her to a strange realm of grey mist and stars, where two mysterious girls appear before her.

With no understanding of her new power, Yuna takes on a mysterious identity:

Shadow.

And thus, her journey into the world of mysteries begins.