It all began on a summer night aboard a cruise ship with Jun and Ippei. Yuriko first sees a UFO, then finds a strange doll on deck. The doll identifies herself as Zerni, a member of an alien race, and reveals that a violent monster's egg has fallen into the sea. Jun and Ippei don't believe Yuriko until they speak with Zerni themselves. Zerni explains that the monster must be hunted down.