A young man who failed the exam was forced to get involved in the trend of working. However, he had a foot problem and faced obstacles in finding a job. After several setbacks, he entered a factory. But he met an ordinary and enthusiastic woman by chance. The two of them share the same spirit of learning and progress and love each other. However, he discovered that the woman already had a husband. After being disappointed, he was moved by her crying about the misfortune of her marriage and became even more sympathetic to her. From now on, they are classmates? A friend? A lover? However, they chose to be the fourth confidant, the blue confidant.