Xiao Yu

She grew up in a poor family, but was discovered by Zai-jan and became his mistress.
She sympathized with John's attempts to correct the wrongdoings of high-ranking government officials and provided him with information.
She also introduced John to her uncle, Seraph, who had emigrated to the U.S. to help John defect.
At this point, however, she did not know that Seraph was a CIA agent, but thought that he was a well-connected writer.
After John's death, she became a CIA trainee because of her quick wit and energy.