Lucy's mother was raped, and held captive until she gave birth to Kaede, where she then comitted suicide. Her father, disliking how Kaede had horns (and was not human) had left her at an orphanage. She grew up in the orphanage being tauned for her appearance (having two horns) and was bullied mainly by about a group of 3 - 4 boys. She had only one friend, a homeless dog which she fed some of her food to. She told another girl about the dog, and the girl tells the bullies. The bullies confront Kaede, where they then beat her dog to death, activating Kaede's (Lucy's) sadistic serial killer personality, where she then slaughters all of the boys and the girl. She meets a boy named Kouta, who thinks her horns are 'cool' (just as shes about to kill him) She at first rejects his friend ship, but then be friends him. After a few days, Kouta tells Kaede that he's leaving, and going to a carnival before he leaves. He tells her that he is going with a cousin, where she asks him if it's a boy or a girl. Kouta, trying not to hurt her feelings, tells her it's a boy (even though it's a girl) She promises to say goodbye to Kouta at the train station when he leaves. But instead, she goes to the faire to see if her friend was lieing to her. He was, and presuminbly, Lucy's concious tells her to start killing again. She slaughters alot of people around her, where Kouta's little sister (Kaene) sees her. When Kouta is on the train, Kaene tries to say that 'she saw a horned girl in themiddle of it' where Kouta dismisses what she's saying as lies. As Kaene is standing at the end of the carrage, Lucy (Kaede) gets up from a seat, and Kouta is happy to see her. Kaede proceeds to kill Kaene and Kouta's father, and says shes going to go and kill Kouta's cousin, Yuka. He stops her by knocking her back into her non-serial killer personality.

In the OVA episode (episode 10.5) there's another flashback of Kaede's past. She's with a friend, most likely another run away and says shes a wizard, not knowing who she is or how she possess her powers. The two are confronted by soldiers, where they open fire (and Kaede protects herself and her friend) But from the side, another person comes and shoots her friend. Kaede makes a deal with Kurama to go with them without a fuss, and they'd do what they could to save her friend. She ends up dieing from the gunshot wound, where Kaede then makes a vow to take everything away from Kurama to make him feel like she does.

The past events happened when Kaede (Lucy) was a child, so there's notan exact amount of years that she was in the militay facility, but it's (in my opinion) about 10 or so years. They studied her, and tested on her. She eventually broke out (in episode 1) In episode 13 (last episode) Kaede tells Kouta that she only managed to keep sane by the need to apologize to Kouta for killing his family. In her escape attempt, Kaede is shot in the head (through a metal helmet) making her lose all of her memories. This is where her alter-personality, 'Nyu', is born. She can turn back into a sadistic serial killer by being violently attacked or by hitting her head. She often tries to stay as Nyu, and if turned into her serial killer self can be turned back by the want to not hurt Kouta.