A young Taiwanese assassin codenamed "Glass Heart" committed suicide by jumping off a building, and her heart was pierced by a metal fence. Miraculously, her life was saved by heart transplantation. During her recovery, she began to experience strange dreams, which led her to Japan to look for the donor of her heart, who happens to be Kaori Makimura, former partner of City Hunter. Angel Heart shares the same characters as City Hunter but is not its continuation. Therefore, the events take place in a parallel universe.