Yang Sizhen is the daughter of a deputy commander and an underground worker. Yang Siyan appeared in the fourth episode. Under the arrangement of director Li's appearance, Sizhen and Wu Dacun met. When we met, we didn't talk too much, but went straight to the subject and talked about the intelligence agent arranged by the Japanese. Yang Sizhen told Omura that they were in a very critical situation, and there must be enemy undercover. At the end of the war, Yang Sizhen provided Wu Dacun with the news of Japanese officers' trucks coming in and out, and told them that these officers came from different regions, which made Da Cun highly vigilant. After all kinds of intelligence summary and comprehensive analysis, Omura concluded that these trucks must have come for Qinyuan. With this analysis, Pei Yong was very happy, so he studied overnight and laid a big net for the Japanese, trying to beat the Japanese delegation out of the water. In the battle, Wu Dacun died heroically in pursuit of Keiko Miyazawa. Yang Sizhen saw Wu Dacun sacrifice in front of her and killed Jing Shangjing and Keiko in a rage. At the same time, Ou Yangchun was ordered to open up base areas, and the news that they defeated the Japanese delegation reached the headquarters. Li Da immediately reported the news to the headquarters of the Eighth Route Army in Yan 'an. At this point, Chiang Kai-shek was startled by the armed forces of the Chinese Communist Party after seeing the report of the war situation, and a chill rushed to his head.