Yukina is the kind, thoughtful, and somewhat naïve twin sister of Hiei. Her name literally means 'Ice Sprout'. Yukina was born as an ice apparition (Kourime, literally ‘Ice Woman’), the same as her clan. Ice apparitions have special abilities relating to snow and ice, and have light healing abilities. In addition, when they cry, their tears become gems, which are highly valuable in the human world. But she was also born with a twin brother Hiei. Her twin brother was the forbidden child who was never supposed to exist, and was "killed" by being thrown off a cliff, despite his mother's desperate pleas.

At the beginning of the series, Yukina had no knowledge that both Hiei existed and that she had a brother. Hiei also, for reasons that remain largely unknown to Yukina, always shows up at various times to protect her when others aren't around or are unable to do so. In the manga, Yukina does eventually figure out that Hiei is, in fact, her brother. (In the English Dub Hiei often tells her that her brother is most likely dead) Yukina is also the love interest of Kazuma Kuwabara, although she remains unaware of this. The very first time Kuwabara saw Yukina via video tape, Kuwabara replied that he was in love and left quickly to rescue her, although he didn't stay long enough to find out that Yukina was Hiei's sister. At any time he can, Kuwabara will try to protect Yukina at any cost to him. At the very first sight of Yukina, Kuwabara's strength rapidly increases past its normal limits, as seen during his battle with Risho. After seeing how Tarukane treated Yukina, Kuwabara told her he wanted her to not hate humans, to which she replied that she didn't dislike humans and liked Kuwabara.