Yuuki

The heroine of the Mother's Rosario arc. She refers to herself as "Boku." Born on May 23, 2011, she has traversed various VRMMOs and is known as "Absolute Sword" in the new ALO, boasting overwhelming strength. Despite not using the Dual Blades skill, she is the only person to have defeated Kirito twice.

Infected with HIV from a blood transfusion at birth, she has been battling illness since childhood. Her parents and twin sister have already passed away from AIDS, leaving her alone in the world. She became the first test subject for a medical virtual reality machine and has spent the past three years in the virtual world. Her extraordinary combat abilities in ALO stem from her long-term medical dives.

After her sister's death, she took over as the leader of the Sleeping Knights but was also given a prognosis of only living until the end of 2025. To create her final memories, she appeared in the new ALO on New Year's Day 2026, engaging in duels to find allies for a boss battle, wagering her original sword skill "Mother's Rosario." She met Asuna, who was intrigued by her victory over Kirito, and requested her help. After successfully defeating the boss, she saw her sister's image in Asuna and disappeared from ALO out of guilt.

She was slightly wary of Kirito, possibly because he saw through her origins, but confided in Asuna, who visited her in the hospital with Kazuto's information, expressing her wish to attend school. Using an audiovisual bidirectional communication probe created by Kazuto and others, she attended school with Asuna. She later became friends with Kirito and faced him again in the finals of the new ALO's Unified Duel Tournament, defeating him to win. She enjoyed a trip to Kyoto with Asuna and others, but her condition worsened on March 29, 2026. She entrusted "Mother's Rosario" to Asuna and passed away peacefully in her arms, surrounded by the Sleeping Knights, Kirito, and many players she had interacted with.

In the Underworld, her phantom appeared in Asuna's memories during her STL dive, fighting alongside her against PoH and advising those who come to the virtual world on what they seek.