Kato, Shimura, Arai, Nakamoto, and Takagi are friends at an all-boys boarding school. After they get tricked by their school government president, the five must put on a performance of the play "Little Women."

Episodes based on Mikoto scenario.

Naoki Kuzumi, a junior in high school, had lost his parents in an accident five years ago, and is living with his aunt, uncle, and cousin Matsuri. He always thought his life was ordinary, besides the fact that he can't remember what happened in his youth. One sunny day as he is taking a nap on a bench, a redheaded girl -- Mikoto -- literally falls on him from the sky. For some reason, she thinks he's her younger brother. Naoki's time period is a temporal shelter for those in the future, when many are suffering from an incurable disease. When she heard her younger brother Yuusuke had been taken to Naoki's time, Mikoto herself had gone back in time.

A young Taiwanese assassin codenamed "Glass Heart" committed suicide by jumping off a building, and her heart was pierced by metal fence. Miraculously, her life was saved by heart transplantation. During her recovery she began to experience strange dreams, which lead her to Japan looking for the donor of her heart, who happens to be Kaori Makimura, former partner of City Hunter Ryo Saeba. The author mentioned in the first tankoubon volume that Angel Heart only shares the same characters of City Hunter but not its continuation. The events are all parallel universe, therefore it has nothing to do with City Hunter.