

After the baby was taken out of the womb, a barcode containing the numbers 20320930 was imprinted on the newborn's neck, symbolizing the birth date of September 30, 2032. Using another Fluctlight taken from somewhere else, she inserted the foreign Fluctlight into the baby's brain, overwriting the existing one. However, once the baby reached the turning point of its development, Shikimi rewrote the baby's soul. Combining an egg and a sperm through In Vitro Fertilization, she and another researcher birthed a baby inside an artificial womb. Disregarding all ethics, one researcher by the name of Shikimi Kamura did exactly that. However, the other company, KAMURA, took things one step further: they sought to copy and paste the human soul. Using this newfound technology, RECT created and released the Neurolinker. Seeing the vast potential of STL-T, two competing companies researched the field at the same time: RECT and KAMURA.

Through this miraculous new technology, the souls of human beings, also known as "Fluctlights", could be read. In the late 2020s, Soul Translator Technology (STL-T) began to arise. However, even though they show romantic feelings towards each other, they become serious when fighting against others or giving each other information. The two are so close, in fact, that she has promised to stay by Haruyuki's side forever in spite of the unfathomable risks that exist in Brain Burst. She also loves Haruyuki, and their friendship grows to the point where she acts as his spouse despite her role as Legion commander and Silver Crow's parent. However, she later admitted to using Brain Burst to beat his score. She seems to be a hardcore gamer, especially simulation games, as she defeated Haru at his favorite game of squash by achieving more points than him. When she doesn't know someone's name, she will address them as "boy" or "girl", as she did with Haruyuki when the two first met and for a time afterward. During her time as the "Black King", she killed the previous "Red King" and also tried to kill the other members of the "The Six Kings of Pure Color" in order to reach level 10 and find out who the creator of the Brain Burst game is. Kuroyukihime boasts of herself, confident in her nature. Unsurprisingly, she is also a good strategist.

Brain Burst is not her only area of expertise, however, showing proficiency with the infrastructure of networks and deducting information, even knowing the steps undertaken by the networks that have been used. She shows wisdom and experience, being deeply knowledgeable about Brain Burst due to her time as the "Black King". She also has a habit with hypnotizing wordplay, which others find to be an annoyance.

She is also shown to be somewhat impatient, having created an app that maps the shortest path through a supermarket to get all the required items, even considering adding an automatic payment function so users can walk right out of the supermarket. Like any human, however, Kuroyukihime can sometimes be rude, angry, or even jealous - especially when other girls flirt with Haruyuki. Kuroyukihime has virtuous tranquility and patience. It is somehow known that she prefers to wear black colored clothes. It is extremely rare to see Kuroyukihime in casual clothing. As she moves to her final year at school, her uniform alters to a red bow tie with all else being the same. Her wardrobe is usually her school uniform consisting of black tights, a dark green skirt with a brown trim, a navy blue blazer, and a light blue bow tie. When Kuroyukihime was hospitalized, she had her hair in a ponytail. Holding true to being "the most beautiful girl in school," Kuroyukihime is a very attractive and slender young girl with long black hair that has two strands of hair extended from the top of her brow, resembling the antenna of a butterfly and large hazel eyes.
