Atsuko Sasaki

Atsuko Sasaki (佐々木 敦子 Sasaki Atsuko), commonly known as Acchan, was Katarina Claes's best friend in her previous life.

It's eventually revealed that she reincarnated into a friend of Katarina in the present, Sophia Ascart.

Appearance
Atsuko has brown eyes and hair Her hair is in medium length with short bangs, with some of it tucked to the front of her left shoulder. She is typically seen wearing a normal high school uniform.

Personality
Atsuko is an introvert who has a hard time befriending her classmates. She is seen as an oddity by students around her as she usually kept to herself, leading her to be bullied. She has a very active imagination, often visualizing herself as the protagonists of books she's read in order to escape reality.

After becoming friends with Katarina, she's grown to be a much more sociable person, who can easily drag people into joining in her interests. Atsuko adores talking about the things she loves, and she can't restrain herself when talking about spoilers and plots of the series that she's into.

Background
In elementary school, Atsuko was often teased, ignored, she had her stuff hidden and she was kept out of the loop by everyone that this caused her to become recluse and afraid of other people. At thirteen, she enrolled in a local middle school and nothing had changed despite it being a new environment. Instead, Atsuko spent her days reading all kind of books as an escape for feeling lonely. Her daily routine stayed the same for weeks - going to the library to borrow books after homeroom, changing her shoes at the shoe lockers then cutting across the courtyard to head for the school gate.

However, after seeing other girls chatting while crossing the courtyard, thinking how nice that would be, Atsuko was hit by something with a tremendous impact and instantly fell unconscious. It turns out that a person fell on her. The person being the previous reincarnation of Katarina Claes. She apologized, saying that the charm of the tree was too strong that she couldn't resist and that her foot slipped.

After ensuring the girl that she was fine, it turns out that they were in the same class despite Atsuko not knowing who she is. She introduces herself (although does not reveal the name) and before Atsuko realized it they became friends.

Before Reincarnation
Both Atsuko and the girl were otaku and worked in a part-time job together. She would always support her whenever she forgot her homework and thought that her days would always continue like this - full of life and energy. However, that girl was absent from school one day. But, Atsuko didn't think much about it until she found out after school that she took all the days for granted. She couldn't believe what happened and held onto the hope that she would return.

The days went on normally and looking at her messages, one was unread and sent by her best friend. It was sent in the middle of the night on the morning she died, the message was: "Acchan, I'm having trouble capturing the sadistic evil prince~" Atsuko finally cried and accepted the truth that the girl would never return. Although she was very sad about her friend's passing, she was very thankful to her for opening a new and brighter world. She wished that when her life is over, she could be reincarnated into a new life with that girl and be friends again.

Reincarnation
Atsuko's memories of grief return to Sophia as she and Katarina's other friends stand vigil when Katarina is in a magically-induced coma.

Unnamed Girl
She is Atsuko's first friend since middle school. As Atsuko was a shy girl who didn't know how to make friends, she was easily drawn to the girl's charm and optimism. Atsuko would often her the girl with studying and school work as they talked about their similar interests. She isn't exasperated by her friend's antics, as she found it very funny. Their classmate's and the girl's parents would often thank Atsuko for setting her friend straight and for changing the "monkey girl" into a more "human state".

Etymology
Sasaki (佐々木) means "help, aid" (repeated, indicated by the iteration mark 々) and 木 (ki) meaning "tree, wood"

Atsuko (敦子) means "honest" (敦) (atsu) and "child" (子) (ko). Depending on the writing, Acchan's given name can have various meanings, such as "warm child" (温子) or "passion/heat child" (熱子)

Trivia

 * Despite being reincarnated as Sophia, Atsuko can still her reincarnation's decisions and shows awareness outside of herself.