Suguha Kirigaya

The heroine of the Fairy Dance arc. She is Kazuto's younger adopted sister by one year (biologically, she is his cousin) and is called "Sugu" by him. Her birthday is April 19, 2009, in the story. Although she is petite, she has an estimated E to F cup size, which is a secret source of concern for her. This development occurred rapidly during her growth spurt over the next two years, and at the time of the SAO incident, she had a similar appearance to Silica, whom Kirito saw a resemblance in. She has been diligently practicing kendo for eight years since childhood, achieving the top 8 in the national competition in her last year of middle school, and being selected as a regular player in the inter-high competitions as a first-year student at a prestigious high school.

Kazuto and she were close siblings when they were young, but they grew distant after Kazuto quit kendo. The SAO incident made her regret her previous relationship with Kazuto and she sought to bridge the gap. At the same time, her mother revealed that she and Kazuto were not biological siblings, causing her to struggle with their relationship. To understand the world Kazuto loved, she ventured into the online gaming world she once disliked.

In ALO, she is a skilled player, ranking among the top five in her race due to her real-world sword skills and reflexes. She is saved by Kirito, who came to ALO to find Asuna, and without realizing each other's true identities, she volunteers to guide Kirito to the World Tree, supporting his quest. She becomes attracted to Kirito while fighting alongside him and realizes her romantic feelings for her brother in the real world. Despite continuing to harbor feelings beyond sibling love, she steps back upon realizing the depth of Kazuto's feelings for Asuna. After the old ALO incident, she starts calling Kirito "big brother" in the game, and their sibling relationship remains good in the real world, although she still has lingering feelings for him as a member of the opposite sex.

Her avatar in ALO, based on her self-image, has blonde hair and green eyes in a ponytail, with a bust size similar to her real self. She primarily uses a long sword and can wield some two-handed sword skills with both hands, in addition to one-handed sword skills. The long sword is a weapon type that is light for a two-handed sword but heavy for a one-handed sword, making it a perfect fit for Leafa, a kendo club member. In UW, she uses the one-handed sword-type GM equipment Vardulas Anima, and in UR, she equips a long sword, a green dress, and the same metal armor as Kirito.