Leafa, known in the real world as Suguha Kirigaya, is the cousin of Kazuto Kirigaya, raised as his sibling after his parents’ passing. Honing her kendo skills from childhood, she achieved national quarter-finalist status, a foundation that later elevated her combat prowess in virtual realms. When Kazuto withdrew into virtual reality upon learning they weren’t biologically related, she entered ALfheim Online as Leafa to reconnect with his world.

In ALO, Leafa excels as a Sylph warrior renowned for aerial combat mastery, earning the moniker "Speedaholic" for her relentless pursuit of flight techniques. Her avatar sports long blond hair, emerald eyes, and armor combining white, green, and silver elements. During the Fairy Dance Arc, she allies with Kirito, unaware he is Kazuto, until a revelation sparks emotional turmoil. Their climactic duel resolves into collaboration to free Asuna, cementing their bond.

Within Project Alicization, Leafa assumes the Terraria superaccount, wielding amplified powers to aid the Underworld conflict. She clashes with foes like the Dark Mage Dee Eye Ell, leveraging combat intuition and forging alliances with figures such as the Orc Chief Lilpilin, whose defiance of programming underscores her ability to unite disparate factions.

Throughout the War of Underworld, Leafa’s unwavering loyalty to Kazuto and protective instincts mirror her kendo discipline and upbringing. Facing trials like Kazuto’s comatose state and chaotic battles, her resilience shines. She strategically integrates real-world swordsmanship with virtual aerial tactics, becoming indispensable in large-scale warfare.

Her evolution spans arcs like Girls Ops, where interactions with fellow heroines highlight her leadership and empathy. Leafa’s journey navigates familial bonds, self-discovery, and ethical dilemmas bridging virtual and real worlds, anchoring her role as both warrior and mediator.