Insanity's Ideals ~Prequel to Deathnote~

Before Yagami Light became Kira, there was another before him. A story locked away and forgotten by everyone expect one. Tagiyoshi Ai was never a very talktive person; she chose to keep to herself. She is obessed with human activity and dreams of becoming a mentalist, despite her one flaw of hating humanity. One day, her life changes when she picks up a strange book that she found while walking home:
Deathnote.