She is Tomo, Misao, and Kanade's senpai. She was also involved in the plane crash 3 years ago, and nearly died. Her limbs have been replaced by machinery after the accident, thus making her able to store weapons in her arms an legs. After her sister gave her soul to the Asura Machina, she've been trying to find a way to save her. Due to her calling her sister Shuri, even though her sister's name is Yukari, it's unknown if Shuri is really Shuri or her twin sister, Yukari.
It's been confirmed in Episode 12 of the second season (Episode 25 of Asura Cryin') that Shuri swapped her soul with Yukari's in order to protect her from becoming a Burial Doll