An Si-eun

An Si-eun (also romanized as Si-eun An), known in-game as Siune in ALfheim Online (ALO), is a supporting character who appears in the Mother's Rosario arc of Sword Art Online II (the anime adaptation covering volumes 7 of the light novels).

In the anime, she is portrayed as the second sub-leader (or vice-leader) of the Sleeping Knights, a small guild made up of terminally ill players who originally connected through a palliative care VR program called Serene Garden. They play various VR games together to enjoy life and achieve something meaningful despite their conditions.

Siune is a calm, supportive, and level-headed member of the group, often acting as a reliable second-in-command to the guild's leader, Yuuki (the "Absolute Sword"). She uses a support-oriented playstyle in ALO and helps coordinate the guild's efforts to leave their name on a high-floor boss as a final goal.

In the real world, she is shown as a young woman who has been battling illness (acute lymphoblastic leukemia in the source material), wearing glasses and a wig due to chemotherapy effects. She survives her condition by the end of the arc and appears in a post-arc scene meeting Asuna outside the hospital.

She's a kind, loyal friend to the Sleeping Knights members and forms a meaningful connection with Asuna during the events.