Katsumi is the daughter of Gigelf Liqueur a magician that tried to open a gate to the alternative world Nemesis. This experiment failed and lead to the Nemesis race, Lucifer Hawk, to infiltrate earth. Katsumi herself finds out that she also possesses these magical abilities and gains the sentient sword, once wielded by her father, Grospoliner to fight these beings. After discovering her magic abilities she joins the AMP, a special branch of the Tokyo police force. Her personality is by nature gentle but she is also harsh and she may don't think twice before rushing into battle. Through her veins runs the blood of a Lucifer Hawk something that could be seen as a blessing but Katsumi can't bear it. As a result of Katsumi past life she don't find it an easy task to let people into her life and when she first arrives in the AMP group she becomes the drawn back one that keeps herself in her corner. She quickly starts to get along with the people there and at a party where people form the normal police force are invited she meets her soon to be boyfriend Roy.