Diana A. Xayasith or "Sis" is a human nurse who was the primary caretaker of Five in the Lab. She is a student of Prof. Lumen, and was instrumental in keeping research unit going in spite of previous experiment failures.
Diana has strawberry blonde hair tied into a bun. Underneath her lab coat attire, she wears a green sweater, purple miniskirt, black leggings and purple loafers. She wears a pair of round glasses. Her eyes are light green.
When Five was very young and sickly, she was transported to a human hospital by Sis. There, Sis took care of her and her condition gradually improved. She played with Five every day and read her stories that Five still recalls with great detail. Sis seemed to dislike the ongoing royal disputes between Princess Ruta and Prince Suvillan III at the time, and tried to distract Five from it as much as she could.
At one point, Diana arranged a birthday party for Five with the presence of Solis and Lune. After Five's birthday, Sis, along with everyone else were gone for unknown reasons and the hospital was in ruin. It is unknown what the current status of Sis is.
She enjoys taking care of Five and reading her stories, though she dislikes the grim endings of those stories, and chooses to make her own. She displays a more loose, carefree side when throwing a birthday party for Five. She's also a bit of an alcoholic.
- Diana is a Latin name whose origins can be traced back to the Proto-Indo-European dyeu or dyius, meaning "day" or "sky", as well as "divine" or "godly".
- Diana is the Roman form of Artemis, Greek goddess of the moon and the hunt, protector of children and women in childbirth.
- She is implied to have committed suicide with a noose.
- She is associated with red spider lillies. Spider lillies symbolize goodbyes, people parting ways for good, abandonment, and death.
- She's not the only female blonde human to try altering the ending of a story.
- Diana likes to drink and to read children's stories. She also likely enjoys in partaking in the sciences, such as biology or chemistry. She thinks thrilling extreme sports like mountain climbing could be fun to try sometime, but is too worried to go for it.
- Diana was interested in nykelharpas (keyharps). She liked how complex the instrument is, but wasn't by any means able to find the time to practice it.
- Diana takes alcohol better than Kaji.
- Diana rather it be the day.
- Diana's favorite place is her old lab.
- She has the worst handwriting, apparently her handwriting is like a doctors.
- She along with Five are unable to awaken an ability.