Cloned from Yuuri Kumoi by the organization Black Phantom, Yugiri (also called Yūgiri) was one of the first-generation Phantom Children. An early test triggered a catastrophic loss of control over her psychic abilities, severely injuring overseeing personnel. Fearful of her unstable powers causing further harm, she fled the Monarch orphanage where she was placed after the incident, encountering Monarch's Princess, Sophie Grace, during her escape. She was subsequently recruited into the esper organization P.A.N.D.R.A. by Kyōsuke Hyōbu.

Later, imprisoned within a specialized esper-containment facility where authorities planned experiments, Yugiri was rescued during a jailbreak orchestrated by Hyōbu and Andy Hinomiya. She witnessed Hyōbu unleash his full power to defeat a formidable bio-engineered adversary created from esper body parts during the escape.

Yugiri initially resisted others making decisions for her, often sulking to express her dislike. She developed an intense, exclusive attachment and loyalty to Hyōbu, rarely allowing others near and frequently holding his hand, stemming from him saving her from loneliness and a destructive path. Her relationship with Andy Hinomiya began with distrust due to his hidden role as a government infiltrator and his innate power-nullifying ability, which caused esper discomfort. During an amusement park outing under Andy's supervision, public rejection following a power manifestation triggered another dangerous loss of control, plunging her into a hypnotic trance. Andy's intervention to contain the situation marked a turning point in their bond.

Her development focused on overcoming isolation and fear, forming connections beyond Hyōbu with Andy and other P.A.N.D.R.A. members like her bodyguard and friend Magi and Momotarō. When Princess Sophie Grace, recalling her from the Monarch orphanage, offered adoption into the royal family, Yugiri consciously chose to remain with P.A.N.D.R.A., valuing the belonging she found there and solidifying her commitment to Hyōbu and his cause.

In the climax of her known arc, Yugiri played a crucial role when Hyōbu's powers went out of control after freedom from Saotome's mental domination. She willingly risked her life alongside Andy Hinomiya in a desperate effort to save Hyōbu, demonstrating her growth into a loyal and courageous member.

A high-level esper, Yugiri possessed formidable telepathic and hypnotic abilities. She could read multiple minds simultaneously and project complex, lifelike illusions affecting hundreds nearby. However, her youth and inexperience made control difficult, especially under distress. When emotionally overwhelmed, her powers could affect allies and enemies indiscriminately, reflecting their inherent instability despite immense strength.