In the city of Maleville, there lived a fragile girl by the name Kat Aero. One day, she met a mysterious girl who was the same age as her named Mizuki. She finds that the world she knew shattered for eternity. She weeped and cried as she saw a horrid ghostly beast had been slain by Mizuki.
The universe is divided into 3 worlds, Mageo, Earth, and Rifto. Mizuki comes from Mageo, a world of magic and wonders. The people of Mageo are trained with unique magic to kill Riftels, the species of Rifto. Rifto is a dark place full of horrid and ghastly beasts. If the Riftels are to remain on Earth for a certain period of time, they will eventually gain the power to physically kill humans and destroy their race.
When Kat discovers the truth of the universe, she also finds out she was born into a family of royalty in Mageo. Mizuki insists to bring her back to Mageo to join her guild and train her as her power of a royal offspring can potentially destroy even the most powerful of Riftels.