From the back cover of volume 1:

When the Blackthorn group learns that the evil Simon Blankenship is trying to track down one of the ancient Mithrian artifacts in Japan, Rachel and the gang get on the next flight to Tokyo to beat him to it. But will the fate of mankind get overshadowed by the weird tension growing between Alex and Rachel, or how Pilar--Rachel's best friend and Alex's girlfriend--is going to deal with it? And when Rachel's mysterious powers begin popping up, will she finally face the fact that she is indeed the reincarnation of the Goddess Etherea? Packed with deception, adventure and--of course--shopping, the first Spy Goddess manga will make any teen girl want to go into international espionage.