Kurohane had a difficult childhood where in the elementary school, she was teased and bullied by her classmates, calling her Yurei for her looks and antisocial personality. Eventually, she used her powers to kill them via cursed letters created with her blood as ink. She tricks Yoshikawa into reading the letter, and the curse claims her. Kurohane's mother was called in school, informed of what happened, and shown Kurohane's letters. This alarmed her parents about her powers, causing them to fear and neglect her and only care about her younger sister Kana who constantly bullied her. Like Kurohane's previous victims, Kana was also afraid of her to the point she compared her to a ghost, and claimed that her eyes look like skull's eyes.
One day, Kurohane was diagnosed with cancer, but her parents didn't care, stating that it would be better if Kurohane died. This of course, enrages her and Kurohane is broken-hearted and decides to curse and kill Kana and their parents. She writes a short tale and gives it to Kana. She reads it, falls under spirits' influence, begins to suffocate and dies within a month. Then, Kurohane tries to do the same with her parents, but fails due to flaws in cursed writings that she gave them, and enters a competition to improve her skills.
High School Life
In High School, Kurohane becomes the top student in most regards, and gains a reputation for writing. Her senior, Shiori Sonoda, becomes increasingly jealous of her, and begins to hate and fear her, apparently sensing her otherwordly nature. Yuka is mostly indifferent towards Kurohane, if not, slightly jealous too, but tries to be nice to her due to respect, although Kurohane harshly rejects her advances. Chiharu jokingly tells Yuka that Kurohane looks like Sadako Yamamura, not knowing that Kurohane is literally as dangerous as Sadako herself. Sonoda, Fujita, and Miyuki began to bully Kurohane in retaliation to her anti-social personality, still unaware of what she has in store for them.
Testing Her Improved Writings on Her Powers
Sonoda then schemed a plan to humiliate Kurohane further by appointing her to write a script for a school festival, intending to somehow make her look stupid. Kurohane uses this opportunity for revenge, and begins feverishly writing her script. Yuka notices that Kurohane takes the script seriously, and warns her of Sonoda's intentions, but Kurohane eerily reveals that she knows it, and that it is exactly the reason why she's working so hard. Miyuki takes Kurohane's notebook ahead of schedule, reads it, and has a strange reaction, which is noticed by Yuka. Miyuki begins suffocating during class, and is rushed to a hospital.
While everyone talks about Miyuki, Kurohane only continues writing, and Yuka suspects that she is responsible for Miyuki's condition. Yamashita reads Kurohane's script, and falls under spirits' influence. Realizing that something is wrong with it, and that it is responsible for Miyuki's condition, he immediately locks it up in his desk before forbiding anyone to read it. On Sonoda's request, Kurohane writes a new script, imbuing it with her blood mixed with the ink as medium. Eventually, Miyuki dies, and students are informed of her death.
When Yuka asks Chiharu about the curses, Chiharu tries to convice her that Miyuki's death is a coincidence, and that no curse is capable of killing, but Yuka doesn't really believe it. At the same time, Fujita and Chiharu reads Kurohane's script on separate occasions, resulting them cursed and attacked by spirits: Chiharu was killed on that very night, but not before calling and warning Yuka that the curse within Kurohane's script was real, while Fujita begins suffocating during class, and is rushed to a hospital, but dies soon after. Yamashita himself also succumbs to the curse and commits suicide by jumping from the school roof.
Now with dangers of Kurohane's cursed scripts becoming genuine, Yuka warns Sonoda and manages to prevent her from reading the script, causing her to flee in terror upon seeing Kurahane. Kurohane asks Yuka why she interferes. Yuka tries to reason with Kurohane, but fails. Kurohane states that she is dying from cancer, and had tested her abilities by killing Kana, and is going to kill Sonoda, and everyone else for putting her life in living hell (though the way they mistreat her quite petty). She also reassures that her curse will only get stronger after her death. Sonoda transfers to another school in hopes to avoid Kurohane's grasp for good, much to Yuka's relief. But Kurohane doesn't give up: On the very night, she writes, and sends Sonoda a cursed message through the phone, using Yuka's name to fool Sonoda into reading it. Sonoda reads the message, falls under the spirits' influence, and begins to sufocate. Sonoda calls and asks Yuka about the message, and realises that it was from Kurohane. Realizing that Kurohane must be stopped, Sonoda decides to kill her in retaliation and goes to her former school with a kitchen knife. She comes to class and stabs Kurohane in the neck just as she sent a cursed message to Yuka. As Sonoda viciously stabs her to death, Kurohane smiles and gazes upon Yuka for final time, stating that she has done her job before succumbing to her wounds and dying. After killing Kurohane, Sonoda finally succumbs to the curse, and commits suicide.
Return as Ghost
Kurohane's parents were seen smiling in relief during her funeral, believing the threat that she posed to them seemingly over. After the funeral, Yuka receives Kurohane's belongings, including her diary. She reads the diary and finds out about what Kurohane's life looked like. Even so, death only temporarily halted Kurohane's rampage, as she later returned as powerful Onryo, who was now strong enough to kill her parents. Yuka came to school, and told her friends (namely Saki, Yui, Mao, Megumi, and Chica) about Kurohane. They took Yuka's cellphone and found Kurohane's cursed message within it, read it and then showed it to Yuka against her consent. As result, it attracted Kurohane to come for them and she killed them one by one, but since Yuka was the least antagonistic toward her, she saved her for the last. By the time it was Yuka's turn to die, Kurohane appears in the fog and walks under the overpass for Yuka. Kurohane intended to claim her, but then chose to either posses or otherwise influence Yuka to write a cursed short story with her words in it and post it online in the internet first before eventually killing her once she outlived her usefulness.