Li, Xiang Ying

Xiang Ying was only 15 years old at the start of the series, despite looking like she was in her early twenties. By volume 20 of the manga she is already 19 years old, though appearance-wise she has not changed.

Xiang Ying has had very little contact with the outside world, except through her handlers. As a result, any potential situation which she perceives as a threat assessment would meet a harsh response, as evidenced when she nearly kills a man merely trying to pick her up. Not surprisingly, the people around her, Ryo, Saeko, Umibozu, Chin, and even Xin Hong realize they have an upward task in trying to teach her how to function in the outside world.

There are several coincidences between Xiang Ying and Kaori. One, is that the Japanese character for Kaori is pronounced as "Xiang" in Chinese, hence her name "Xiang Ying". Also, her major histocompatibility complex is very similar to Kaori's as their human leukocyte antigen encodings are virtually identical. Because of this, Xiang Ying does not need to worry about her body rejecting Kaori's heart as her immune system has been fooled into thinking her heart is the same.

With Kaori's heart, she remembers all of Kaori's memories, her residence, favorite coffee, quotes, and emotions. Along with these memories she inherits is also the ability to hammer Ryo with Hammerspace weapons if Ryo gets out of line (much like Kaori did), much to Ryo's annoyance. She has also gained the penchant for wanton destruction that Kaori has always exhibited when the latter is infuriated, this is in contrast to her previous tendency to execute her previous missions with stealth and finesse.

Source: wikipedia