Not much is known about the NA version of Prius Online, but Gala-Net describes it as a "3C" or three-character fantasy game. The three characters consist of you and two AI-controlled companions, the Anima and Giga. The Anima is your companion, who grows and advances alongside you. The Giga is a sort of mercenary called forth in battle.
Gala-Net promises more information coming to the gPotato site very soon!