Set in a future where the sky has been changed into a giant mirror, two teenage children are caught in a struggle between a group of super-powered beings and a mysterious woman's team of children aiming to stop them.

Over a decade ago, a group of scientists carried out experiments at the Tomb of Gilgamesh, the supposed resting place of the demigod subject of an ages-old myth. After the work at the "Heaven's Gate" facility was abruptly halted, a terrorist calling himself Enkidu set into motion an incident called "Twin X" which transformed Earth's sky into an enormous mirror. In the present day, two siblings named Tatsuya and Kiyoko Madoka are pursued by the yakuza for unpaid debts and are saved by the Gilgamesh, a team of young men and women who transform into hideous beasts. But when a second group of children, headed by the shadowy Countess of Werdenberg, "rescue" the siblings from the Gilgamesh using psychic powers of their own, Tatsuya and Kiyoko are forced to choose which side to believe in.—Tony Myers