Yuki had no other choice but to keep Ariya, an amnesiac gorgeous woman from outer space, to live with her and Yuki's mom when she discovered Ariya's existence behind the massive comet fell into the Earth nearby their backyard. Eventually, Yuki learned that this peculiar woman they adopted from space is no human at all, but an alien being whose possesses an unimaginable scale of power. One day has come and more unknown beings visited Earth and were looking for the Ultima. Ariya has left no choice but to go with them and surrender. Yuki followed them into there unidentified ship and eventually find herself in another world.