Yuuri is the daughter of the head of Black Phantom and the younger sister of Gilliam. As a high-level hypnosis user, she brainwashes the organization’s kidnapped espers in effort to receive her father’s love. Yuuri uses the code name "Phantom Daughter" when in battle. She initially has three personalities:

"Juli" (ユーリ) - The original personality, referred to as “Mirage” by the others. While stoic and seemingly devoid of feelings most of the time, she is very protective of Nye, her bodyguard.

"Phantom" - A more sadistic personality with hot pink hair who houses the true intentions and feelings of Mirage.

"Kumoi Yuuri" - A shy normal girl with dark hair who is unaware she’s an alter ego. She was created by Mirage to disguise herself as a regular schoolgirl and get closer to The Children.

(Source: Wikipedia, edited)