Crescent Moon Series by Haruko Iida

Mahiru Shiraishi is haunted by images of the Descendent of the Princess in a disturbing recurring dream. There, she meets members of the Lunar Race, a group of vampires, werewolves and vixens who need Mahiru's help to recover their power source that was stolen a thousand years ago in an incident involving the princess. In this howling sci-fi adventure, Mahiru will forge a camaraderie that will determine the fate and of the Lunar Race for all of the dream world!