Suguha Kirigaya, known by her in-game alias Leafa in ALfheim Online, is the younger stepsister and biological cousin of Kazuto Kirigaya. She was raised alongside him as a sister after the death of his parents. Her background is deeply rooted in kendo, which she took up in order to protect Kazuto from the disappointment of their grandfather after he quit the sport. Suguha became an accomplished kendo practitioner, and this training translates directly into her combat abilities within the virtual world, giving her exceptional reflexes and swordsmanship.

Her personality is generally cheerful, outgoing, and optimistic, standing in contrast to her brother's more reserved nature. She is highly social and confident in her daily life. However, beneath this positive exterior, she can be emotionally fragile, particularly regarding her feelings for Kazuto. After he was trapped in Sword Art Online, she developed romantic feelings for him, a source of significant inner turmoil once she learned that he was her cousin rather than her biological brother. This unrequited love and the need to suppress her emotions form the core of her personal struggle and motivation.

Motivated by a desire to understand her brother better and to connect with him after his traumatic experience, Suguha begins playing ALfheim Online with the help of her classmate Nagata Shinichi, known in-game as Recon. As Leafa, a Sylph warrior, she quickly becomes enamored with the freedom of flight in the game, earning her the nickname Speedaholic for her love of high-speed aerial movement. Her primary goal during the Fairy Dance arc is to assist the Spriggan player Kirito in reaching the World Tree to rescue Asuna, unaware that Kirito is actually her brother Kazuto.

Within the story, Suguha serves as a central figure in the Fairy Dance arc. Her role is twofold: she acts as a guide and ally to Kirito in the unfamiliar world of ALfheim Online, and her emotional journey from resentment of virtual reality to acceptance and mastery of it mirrors her personal growth. She initially viewed VRMMOs as harmful because they trapped her brother, but through her own experiences, she comes to embrace them as a meaningful space.

Her key relationships are built around Kazuto. The bond with her brother is the most complex, marked by familial loyalty, deep admiration, and an unresolved romantic attachment that she eventually learns to set aside. Her relationship with Asuna evolves from rivalry and jealousy to mutual respect after she accepts that Asuna is the one Kazuto truly loves. Her friendship with Recon provides her with a supportive anchor outside of her family, helping her navigate both the game and her personal feelings.

In terms of development, Suguha transitions from a girl struggling with her identity in relation to her brother into a strong, independent warrior. She learns to balance her personal desires with her loyalty to those she cares about. Her growth is marked by her victory in a Sylph tournament, which solidifies her standing as a top player, and by her ability to move past her unrequited love and continue supporting Kazuto as a sister.

Her notable abilities stem from years of kendo training, which gives her acute reflexes and sword skills that make her one of the most powerful Sylph players in ALfheim Online. Her combat style emphasizes speed, agility, and aerial maneuvers, allowing her to excel in both ground and flight-based combat. She is determined and fiercely protective, willing to face any danger to help her brother and friends.