Sword Art Online II

Three days later, Siune tells Asuna to forget about ever meeting the Sleeping Knights for her own sake. After school, Asuna meets up with Kazuto, who gives her the address to a hospital where a virtual reality gaming console called the "Medicuboid" is undergoing clinical trials. At the hospital, Asuna meets Yuuki's primary care physician Doctor Kurahashi, who explains that the Medicuboid is designed for patients in terminal care, and that Yuuki suffers from AIDS due to an infection via blood transfusion during her mother's labor complications. She has been put in a sterile room to avoid the risk of further infection and has been permanently hooked up to the Medicuboid for three years. Asuna breaks down into tears after learning that Yuuki does not have very long to live, but Yuuki communicates with Asuna via Medicuboid, verifying that she can hear and see Asuna. Using the AmuSphere in the next room to log into the game, Asuna rushes to the place she first met Yuuki in ALO. Yuuki reveals that the Sleeping Knights are all patients in terminal care, being the reason why they needed Asuna to help them finish one last quest before Yuuki's impending death.