Why is it called "Purple Butterfly" I do not know and I could not understand why till I finish seeing it.
It is blue, if we have to find a color to define the film.
The film is about underground organization composed of Ding Hui (played by Zhang Ziyi) and Xie Ming ( played by Feng Yuanzheng) fighting against Japanese invaders. The dramatic conflict is Ding has fallen in love with a Japanese student named Hidehiko Itami (played by Tour Nakamura) who is also her fellow college mate, returns to Japan but gets back to China after his father's death and becomes leader of killing Chinese underground organizers.
The film also stars Liu Ye who is named Stuart in the film, which appears to be funny to me as it is a bit strang pe that a Chinese boy bears a name of western flavor in 1930s.
Li Bingbing acts in the film but the role (girlfriend of Stuart) she plays is killed soon after the film starts. However there are flashbacks of the scenes she works and gets killed. Her death is one of the lines that pushes development of the film. Stuart does efforts to seek revenge for her. Finally he makes it and the sacrifice is that he dies for it.
It is worth mentioning that the long shot, times of flashback, music by Jorg Lemberg great. The Japanese song to which Ding and Itami dance at almost the end of it denotes their love-hatred feeling.
As to acting, Ding's fear, resolution, confusion are well displayed by Zhang Ziyi. Liu Ye also does an impressive job of acting scenes in which Stuart is tortured.
In a word, Lou Ye is a great storyteller and director.