Chiyuki

The Black-Haired Woman (黒髪の女 Kurokami no Onna) referred to by fans as Onna, is an amnesiac woman taken in by Nona to Quindecim and hired as Decim's assistant. Later, her real name is revealed to be Chiyuki (ちゆき Chiyuki).

Appearance
Chiyuki is a young woman with magenta eyes. She has shoulder-length black hair with a streak of white in the left side of her straight across bangs. Her slender and semi petite figure is accentuated with a black crop top, a mini skirt held by a white belt, and ankle strap heels. She accessorizes with a necklace and a white bracelet.

Personality
Chiyuki appeared innocent but skeptical when she first woke up. However, after she became accustomed to living in Quindecim, she acted as a strong-minded individual who always says what is on her mind whenever she feels it's necessary. She does not hesitate to oppose Decim if she feels there is something wrong in what he says. Also, because she retains her humanity even when all her memories are lost, she can give valuable insights to Decim whenever he is judging.

History
When Chiyuki was young, she liked reading Chavvot with her mother –a story about a boy named Jimmy who falls in love with a deaf girl named Chavvot. She has stated that the moments when Chavvot smiles are her favorite parts.

After her death, Chiyuki became one of Decim's customers. However, unlike the other humans who had no memories when they arrived, hers were intact and she was aware of the fact that she was dead. For this reason, Decim could not provoke her into playing a Death Game and with Nona's permission, he had her memories erased and extended her judgement period. After that, she was allowed to stay in Quindecim and assist Decim in arbitrating.

It is later revealed that she was a young professional ice skater. She had a happy childhood growing up with her mother and father and after reading her favorite children's book Chavvot, became interested in ice skating after seeing the little girl in the picture book ice skate. She became very good and it became her passion. She was shown to live her life to the fullest with many great friends and with a warm loving family. Her career as a professional ice skater also began to skyrocket after she won several awards. However, this all changed when she received a horrible knee injury that took away her ability to skate. When she lost her ability to skate, she fell into depression but grew to realize it was not the fact that she couldn't skate that was so depressing so much as the fact that it was what defined her and after being unable to skate, she felt hollow and empty, as if she was nothing and all of the people she cared about became like strangers, as they did not truly understand her and because she lost the one things she could relate to with them: her ability to skate.

Death Billiards
In Death Billiards, she was simply referred to as the 'The Black Haired Woman' who quietly sits back and observes a judgement game as Decim's assistant.

Death Parade
Her role is further elaborated on in Death Parade; Because she was aware of her death, Decim couldn't judge her. With Nona's permission, her memories were erased and she was assigned the role of Decim's assistant as part of her judgement. She helps Decim understand human emotions and provides insight in passing judgements and reading people's feelings. Despite this, she disapproves of the concept of bringing the darkness out in people's hearts, as she feels the arbiters are creating them instead. Eventually, she began to remember who she was, largely due to her re-reading Chavvot, an old favorite book. As she begins to remember, her body begins to crumble, because humans are not permitted to stay in Quindecim for too long before they are judged. By the end of the series, Chiyuki was required to have judgement passed on her soul, and she was sent for reincarnation.

Decim
Upon Chiyuki's first arrival to Quindecim, the two met and agreed to a contract between them as assistant and bartender. The entire storyline of Death Parade revolves around the growing relationship between the two as Chiyuki serves a term as his assistant. Initially, Chiyuki is skeptic of Decim and his ways of judgement, but ultimately learns to accept them and let them grow on her. Chiyuki and Decim are shown each episode becoming closer and closer to getting to know one another and bonding. Chiyuki teaches Decim about human emotions, and impresses him with her vast knowledge on how humans function. Decim is inspired by her ways of thinking to the point where he even meets with Nona to inform her that he no longer believes that the ways arbiters currently judge is correct. Chiyuki brought to light the idea that the extreme conditions were creating darkness in the hearts of the souls instead of drawing them out.

Later, Decim shows great interest in learning more about Chiyuki's background. When the time comes for him to finally make a judgement on her, the two end up embracing in sadness. Though it is not canon, there is evidence to suggest that Decim had feelings of love towards her, as she was the only being capable to ever make him smile.

Nona
She is Decim's boss and by extension, Chiyuki's. Nona assigned her to Decim as an assistant and while neither have interacted with each other since their introduction in Episode 2, Nona believes she has a somewhat good understanding of humanity but still has much to learn.

Nona sees Chiyuki as a chance to test out and show Oculus and the other arbiters that relations between a human and an arbiter is acceptable on all circumstances and should not be a violation of the laws Oculus enforces.

Mother
Her mother frequently shows up in her memories and the two seemed to have a strong bond. While she had a close bond with both of her parents, her mother seems to show up far more often in her memories, possibly because her father is busy with work, and her mother was the one she regretted leaving behind the most.

Quotes

 * "I'm sorry.. for not valuing my life. I'm sorry.. for not understanding how you felt. For causing you so much grief.. I'm sorry. For not letting you have a proper goodbye.. I'm sorry."
 * "It's not just grief. There are as many emotions as there are people. The fragility of someone who lets their anger get the best of them... The strength to overcome fear because of love... You can't comprehend anything about them."
 * "People aren't as complex as you think they are. They're simple, and they get sad or angry over simple things. That's how they are. They're quickly affected by the littlest things, and live without knowing where they're going to fall down. That's who people are!"
 * "I'm sure it's not wrong for people to want to understand each other. And even if it is, I want us to understand each other."

Trivia

 * The picture book, 'Chavvot' and ice skates play a big part in Chiyuki's identity, Chavvot being an inspiration for her passion of ice skating.
 * She appears to be a decent cook, as seen in Episode 7.
 * She has a closet filled with spares of the outfit she wears when assisting at Quindecim.
 * She is the only character to ever make Decim genuinely smile.