The last 20 mins, WTF? (spoilers)

What on earth happened to this film? It plays until the last 20 minutes as a classic star-crossed love story, with Qing Hong's over-protective father thwarting the romance between her and Lu Jun. Then suddenly we are meant to believe that Lu Jun takes an attack of blue balls and rapes Qing Hong, proving her father right all along. It just doesn't convince.