When the River Styx floods the Spirit World, Koenma, ruler of the afterlife, entrusts the Sphere of Power to the ferry girl Botan to carry to spirit detective Yusuke Urameshi. Yakumo, the exiled king of the long-destroyed Netherworld, returns from banishment in the depths of space with three demon-gods to seize the sphere and rebuild his realm on Earth. Yusuke and his allies have to keep it out of Yakumo's hands before the human world is remade into a new Netherworld.