Yuzuki Hoshimiya "PastMizu"

Yuzuki Hoshimiya, also known as PastMizu, it Mizuki's past self. In her time, she just went through the "sad past" Mizuki went to. At the same time she was about to commit suicide in her world like Mizuki did in the past, Mirazuki messed up one of her spells and accidentally sent Yuzuki to Mizuki's world. Since she was never meant to be in PriPara until after she turned into a ghost, she did not get herself a manager or an image song.

Appearance
Yuzuki has short blue hair tied into two small buns at the top of her head and black eyes.

Fish out of Water
Yuzuki was a normal 10-year-old girl who loved to sing and had perfect pitch. Her mother was a retired top idol in a place called PriPara, her elder sister was a very popular idol, and her father was a producer who wrote all of her mother's and sister's songs, despite not able to enter PriPara himself. Her father promised to write Yuzuki a song when she turned 12 years old. Yuzuki was very excited, enough for her to cross out everyday on a calendar and countdown the number of days left before she could finally get her own image song. However, all her classmates, who were secretly jealous, all ganged up and bullied Yuzuki. The girls would call her names, insult her fashion style and occasionally steal her lunch and feed it to pigeons. The boys were in charge of the physical bullying. They kicked, punched and ripped up her homework. Little by little, Yuzuki started to lose confidence. When she told the teacher, the students would all cover for each other, saying Yuzuki started everything. She felt the whole entire world was against her.

Yuri-sensei
Despite this, there was one teacher at school who listened to her and believed her. That was her music teacher, Natsuki-sensei. That was another reason she enjoyed music lessons over any other lesson at school. Not only was she good at it, but no one dared to do anything to her because they knew Natsuki-sensei was keeping a close eye on Yuzuki. This also caused the bullying outside the music classroom to get worse. Girls would call her "The teacher's pet" and call her a cheater when she got high marks in music class. Yuzuki didn't care. She knew Natsuki-sensei wouldn't be biased about something like that.

Framed for Murder
The closer Natsuki-sensei and Yuzuki got, the more Yuzuki told her about her family. Natsuki-sensei eventually found out about her parents and her elder sister. Yuzuki was unaware, but Natsuki-sensei was her mother's rival in PriPara, and never won a live battle against her once. Natsuki-sensei, who went through plastic surgery, requested to visit Yuzuki's parents. Of course, her mother never recognized her. She visited her frequently and pretended to become "friends" with her. 2 years later, when Yuzuki was out on a class camp, Natsuki-sensei killed her parents and her elder sister with a knife from the kitchen. She was careful and wore gloves to not leave any fingerprints behind. When Yuzuki returned from camp, which also happened to be her 12th birthday, she was devastated at what she saw. She rushed over and shook her mum, trying to wake her up, getting blood on her in the process. While doing so, she heard a bag drop and turned around to see Natsuki-sensei, staring at Yuzuki in shock. Next thing she knew, the police came and arrested her because of the blood on her and the fingerprints on the knife which Yuzuki left when helping her mother cook once.

Lawyer
Little did she know, one of her classmates was actually Mirei. With the whole class against her, Yuzuki never noticed Mirei. She didn't bother remembering the name of anyone in her class at all. After secretly hearing Yuzuki "murdering" her parents from one of the teacher's conversations, Mirei asked her mother to defend Yuzuki, but not telling her she was Mirei's mother. Her mother agreed, and Yuzuki's case was put on trial. Natsuki-sensei volunteered to be a witness and testify what she saw (Yuzuki shaking her mother when she came home from camp), which was a big mistake. Mirei's mother looked into her past and found out about her plastic surgery. After finding her blood-soaked gloves in her house, Natsuki-sensei was arrested and Yuzuki was declared not guilty.

Suicide
However, with her parents and her sister all killed, Yuzuki had no where else to go. Mirei's parents offered to take her in, and Yuzuki agreed. However, she didn't want to live. Her life didn't feel complete without her parents. She forgot all about that song her father promised, and her soul was dead. She rarely ate or slept, and spent countless nights thinking about her parents. Mirei's mother and father tried everything they could, but couldn't cheer her up. Finally, one night, she secretly took a knife into her room. In Mizuki's timeline, she would've committed suicide and become the ghost princess. However, Mirazuki, in her future timeline, messed up one of her spells and sent Yuzuki to the present where Mizuki was.

Past and Present, Fated Meeting
She wandered around aimlessly, trying to find out where she was, until Mizuki, who was doing one of her usual parachutes after Shion hit her towards the moon, landed on her by accident. Mizuki immediately recognized who she was, and talked to Yuzuki. Mizuki realized she had nowhere to go, so she invited her to come stay with her. She now lives with SHiMer in their dorm. However, she keeps her emotionless expression. Whenever Shion, Hikari, Chiharu or Jewlie questions Yuzuki and her emotionless faces, Mizuki covers for her and says she had a sad past. Yuzuki occasionally talks to Mizuki about the past, and they sometimes cry together.

Trivia

 * Yuzuki was supposed to lose her memories after committing suicide of everything that happened after her parents died, which could be the reason Mizuki did not recognize Mirei when she returned as a ghost.
 * Since she did not commit suicide, she recognizes Mirei, but finds it hard to approach her.
 * She secretly ships Mirei and Shion together, although she has one on Shion herself. (#ThatsBasicallyIvanly xD) Due to the fact that she is very expression-less, no one knows about it.
 * She gets along with Mirazuki, not knowing the fact that she was the one who stopped her from committing suicide. Mirazuki keeps it a secret from her, since she didn't know whether Yuzuki would get mad at her or be grateful at her for stopping her.