To defeat the dark guild Oración Seis, Fairy Tail delegates Natsu, Erza, Gray, and Lucy to join members from Blue Pegasus, Lamia Scale, and Cait Shelter in a joint effort. Everyone is stunned, however, when the representative from Cait Shelter arrives: a young girl named Wendy.

With Erza slowly being poisoned to death, Carla reveals that Wendy's powers as a Sky Dragon Slayer can heal Erza, which sends everyone off to rescue their friends. However, Natsu, Gray, and Carla are inhibited by members of the dark guild Naked Mummy.