In the months since the Sleeping Knights earned their spot on the Monument of Swordsmen, Yuuki goes on to make friends with Asuna's friends and the other players of ALO. Yuuki goes on to help the Sleeping Knights clear the 29th-floor boss, attend classes with Asuna, and best Kirito in a dueling tournament. Meanwhile, Asuna keeps improving her grades, pleasing her mother, and arranges a trip to Kyoto with her classmates, guildmates, and members of the Sleeping Knights via the Bidirectional Communication Probe.
In the spring, however, Asuna receives bad news from Dr. Kurahashi: Yuuki's condition was deteriorating.
Upon arriving at the hospital, Asuna learns that Yuuki was now in critical condition, having suffered a heart attack. She was stable for the time being, but she was not expected to survive for long.
Yuuki briefly regains consciousness. As Asuna holds her hand, she realizes that she wants to Fulldive once last time.
In ALO, Asuna and Yuuki met at the island where they first dueled. Yuuki uses what strength she had left to execute her patented 11-hit combo Original Sword Skill, which she names "Mother's Rosario". With the skill transcribed to a scroll, she passes her technique on to Asuna in the hopes that it would protect her. As Yuuki laid in Asuna's lap, the other members of Sleeping Knight come to say their farewells to her, promising to meet her again on the other side. They are joined by Kirito, his party, and countless other players from across ALO, all come to pay their respects to the strongest swordswoman in all of ALfheim Online.
Yuuki says that when she learned of her illness, she wondered why she had been born at all if she was only going to die. She had found her reason for living in these last few months, the most fulfilling in all of her fifteen years on earth.
Asuna promises to meet Yuuki again as she falls asleep for the final time.
A memorial service is held for Yuuki a week later, where Asuna meets An Si-eun, the player of the Sleeping Knight member "Sieun". An suffered from acute lymphoblastic leukemia which had been treated with chemotherapy that ravaged her body, but learned recently that her cancer was in complete remission. She felt guilty that she wouldn't be able to accompany Yuuki, but Asuna assures her that Yuuki would want her to enjoy life and not be so hasty to join her. An is moved by Asuna's words and thanks her.
They are joined by Kirito and Dr. Kurahashi. In addition to discussing the medical applications of the Bidirection Communication Probe, they also discussed the successful test results of the Medicuboid. Thanks to Yuuki, there was enough data to proceed with the next phase of the Medicuboid's development. Kurahashi also reveals that the original design of the Medicuboid was provided by a researcher named Rinko Koujiro. Kirito immediately recognizes the name as the person responsible for taking care of the body of Heathcliff's player during the SAO incident, which could only mean one thing: the Medicuboid was invented by Akihiko Kayaba!
Afterwards, Kazuto and Asuna have a picnic with their friends from SAO, along with Yui, thanks to the Bidirectional Communication Probe. Kazuto ponders about how he always believed it would be beneficial to the world if the real and virtual worlds came together, but as the boundary between them grew blurry, it would be easier for one world to deceive people in the other. Asuna assures him that he is helping people with his research. Kazuto then states that perhaps the duty of SAO survivors was to help to usher in an era in which the real world and virtual worlds came together.