An unknown girl with invisible hands, or vectors, and telepathic powers escapes from a secret facility. The next day two cousins, Kouta and Yuka, find her. But she is different from before. She can only say one word, nyuu. Not knowing anything about her, the two cousins take her in. Kurama, the head scientist from th efacility where she escaped, has sent a merciless man, Bando, after her.

Bando escapes from the hospital, still trying to find Lucy to satisfy his grudge against her. Professor Kakuzawa Yū's decapitated body is found by his assistant and Kohta. While searching for Lucy, Kohta and Yuka develop a fondness for each other as displayed through a kiss. Finally, Lucy is found by Kohta and Yuka and taken back home.