Kitajima Shinnosuke is an Arizona cowboy of Japanese descent. One day, he is sent to Shibuya by an Indian elder named Geronimo to find Imoko, a girl who is believed to have encouraged Geronimo to stay alive when he is depressed. However, finding Imoko in the supercrowded streets of Tokyo's busiest district is not an easy job. Shinnousuke soon finds himself in the middle of a gal (fashionable Japanese girls, often perceived as the society's trashes) circle, Angel Heart. Having a unique but wise mind, he helps to solve the problems which arise between the girls while slowly finding a trace of the mysterious Imoko.