Yee Tai Tai
I am increasingly interested in the character of Yee Tai Tai. What kind of wife would go out of her way to move a beautiful young woman into the house she shares with her husband? (Good idea! What could possibly go wrong?) If you watch carefully, it becomes clear that Yee Tai Tai is doing everything she can to promote the affair between her husband and Wong Chia Chi. She brings Wong CC into the house, she provides her with "gaudy" blue fabric that she knows will catch her husband's eye, and she is strategically out of the house at just the right moments. Mr. Yee is able to have dinner with Wong CC because his wife has "a headache from too much mah jong!" (Wong CC uses a fictitious headache later to stay in the house, available to Mr. Yee.)
What could Yee Tai Tai's motivation be? I can think of several.
1.) She may be fed up with Mr. Yee's sexual tastes, and looking for ways to keep him entertained elsewhere.
2.) She may want her freedom to pursue her own affairs. Notice her hungry look when she checks out the handsome young student leader (as Wong CC remarks, "Yee Tai Tai, you're so observant!"). Watch the seductive way she moves as she walks in front of him, while he walks behind carrying her packages.
3.) But I think the main reason she throws her husband together with Wong CC is that this is how she supports her husband's ambitions, which of course enrich her as well. In China, getting ahead is all about social connections. The wives, with their "trivial" mah jong, are keeping the social gears greased. As Yee Tai Tai says, "the Wang government is run by us wives!" and she's not kidding. One wife is busy finding jobs for her husband's relatives. Another wife is counting on Wong CC for the stockings that are hard to get in wartime. I think the student leaders chose "import/export" for the fictional Mr. Mak's business knowing that it would be an irresistible draw for these acquisitive wives.
"Lust, Caution" reminds me of "Barry Lyndon" in this way. In both movies, an outsider attempts to penetrate a world of wealth and privilege. But in both cases, in spite of all the outsider's cleverness and persistence, the rich ultimately close ranks. The outsider is defeated and the rich continue as before.