Amnesia opens with a young woman waking in the back room of the café where she works, unable to remember her own life or the people around her. Cut off from her past and forced to move through familiar places as if they belonged to someone else, she is accompanied only by Orion, a spectral boy visible and audible to her alone. Orion explains that his accidental arrival in her world is tied to the disappearance of her memories, and he becomes both guide and witness as she starts to reconstruct what was taken from her.
Trying to hide her condition, she is pulled back toward Shin and Toma, the friends who first help her, and then toward Ikki, Kent, and a mysterious man who keeps his distance while seeming to watch her every move. As she meets each of them, the pressure on her fragile search for answers grows, and every new fragment of the past deepens the tension around her relationships, loyalties, and feelings. Amnesia turns memory itself into a source of danger, where remembering can expose hidden motives, complicate trust, and change the meaning of every bond she thought she had.