Ruka

Ruka presents herself professionally as a nurse, but her participation in the tournament is compromised by her willingness to cooperate with corrupt officials. She uses medical authority to make an unfair restriction appear legitimate.

She is confident in the strength of her barriers and initially assumes that the fighters trapped within them will be unable to interfere with the tournament.

Her later manga appearances move her away from an antagonistic role and place her alongside the tournament's other female staff members.

Ruka specializes in creating powerful barriers. She can establish a sealed field around targets and maintain it strongly enough to prevent high-level fighters from immediately escaping.

Her barrier is used against Hiei and the Masked Fighter while both are recovering from earlier exertion. The technique is sufficiently effective that their team must proceed without them.

As the Dark Tournament's nurse, Ruka also possesses medical knowledge and is responsible for examining competitors, although her most significant contribution to the story comes from her barrier techniques.

Ruka appears during Team Urameshi's increasingly manipulated progression through the Dark Tournament. Tournament officials arrange for her to declare Hiei and the Masked Fighter medically unable to participate.

She surrounds them with a barrier, preventing either fighter from assisting during Team Urameshi's battle against Team Masho. This contributes to the severe numerical disadvantage imposed on Yusuke's team.

Hiei eventually breaks free after recovering enough power, ending Ruka's ability to keep him contained.

At the end of the manga, Ruka joins Koto and Juri as the "Cult Trio," and the three become popular television personalities in the Human World.

Hiei is one of the Team Urameshi fighters Ruka confines within her barrier during the Dark Tournament.

Genkai, competing as the Masked Fighter, is also confined by Ruka while recovering.

Koto is another member of the Dark Tournament staff. She later joins Ruka and Juri in the Cult Trio.

Juri works as a tournament referee and later becomes Ruka's fellow member of the Cult Trio.

Jin is revealed in the manga to be the fighter Ruka has developed a crush on.