Saeba Ryo, the lead character of "City Hunter," comes off as an easily flattered guy. His true identity is that of a city hunter - a brilliant sweeper. Upon request, he sets out on the streets to "sweep" away the bad guys and teach them a lesson. This is how he earns a living. His partner Makimura Kaori takes care of him and they do everything they can to be there for each other. "Angel Heart" begins where these two find themselves in a desperate situation - Kaori suffers a freak accident, which leads to her untimely demise.
In the midst of all this, a mysterious beautiful girl named Xiang Ying enters Ryo's life. It turns out that Xiang Ying is a heart transplant recipient, and the heart that she received belonged to the brain dead Kaori. Xiang Ying got another chance at life, thanks to Kaori's heart! Just what is Xiang Ying's true identity? As Kaori lives on within Xiang Ying, what will become of her relationship with Ryo?