Due to the recent occurrence of the Sword Art Online Incident, few people were willing to test the FullDive machine's capabilities, though the requirements of careful maintenance and clean location for the Medicuboid would result in a drastically reduced risk of infection for the patient. In February 2023, after contracting esophageal candidiasis, Yuuki received an offer from Doctor Kurahashi to test the first experimental Medicuboid prototype, which had just been completed. For the next year and three months, she underwent severe procedures to treat the infections her body was no longer able to resist. At that moment, Yuuki's immune system began collapsing, resulting in her being hospitalised after contracting pneumocystis pneumonia in 2022. As rumors about Yuuki spread around the school, she was forced to transfer schools. Although Yuuki continued to fight the disease, a group of students during the course of her fourth grade discovered that she was a carrier of HIV. By the time the virus was detected, the entire family was already infected. However, the blood was tainted with the Human Immunodeficiency Virus (HIV), which may result in the development of the Acquired Immune Deficiency Syndrome (AIDS). An accident during this operation caused a large amount of bleeding and thus a blood transfusion was necessitated. Due to dystocia, a caesarean section had to be performed. She believed some things must be done in forceful means for the other party to understand. Yuuki was the kind of person willing to live life to the fullest even in her critical condition, when she died peacefully in happiness. She wore obsidian chest armour, a bluebottle violet tunic and a windswept skirt of the same colour beneath the armour. In ALfheim Online, Yuuki's avatar was a slim Imp with milky white with a hint of purple skin, lustrous and gorgeous, long, purplish-black hair, and red eyes. Yuuki had short, black-brown hair and, in the final moments of her life, she had extremely pale skin, which made her look very sick.