Kyuo was a former member of the Septia troupe Phantom, a group of trained hunters who tracked down demon-beasts, capturing and taming them for use in society. Her grandfather, Jin Stolla, was the leader of Phantom and considered to be one of the greatest Septias ever. When Phantom decided to go after the legendary demon beast, the King of the Moon, they had no idea what they were up against. The King of the Moon, whose powers of strength and regeneration were unstoppable while under the moonlight, destroyed an entire village. The Phantom unit tried to stop the beast but they were all wiped out just in one night. In the morning, Kyuo found the corpses of her teammates and buried them.