In fact, the main reason is that Liu Shun wants to avenge his family. Anyone who has watched TV series should know that Liu Shun's sister was killed by Sakata, when the Japanese surrendered. Sakata and other Japanese want to return to Japan by boat. The water tower was the best place to attack Sakata at that time, so Liu Shun boarded the water tower and aimed his gun at Sakata.
However, Liu Shun did not kill Sakata in the end, but broke the flagpoles of Japanese ships. With the fall of all flags, Liu Shun's gun aimed at Sakata again, and the urn in Sakata's chest was directly broken by a gun. But at this time, the Kuomintang opened fire on the water tower, which was smashed, and Liu Shun ended his glorious life. Subsequently, Chen Dalei took off the right white flag covering Liu Shun's body and set off with his new Fourth Army.
In fact, it is not difficult to see that Shunshun had a full chance to kill Sakata and even more Japanese, but in the end he didn't do so, because he was an organized and disciplined soldier, and he knew that he had a more important mission, but Shunshun just couldn't get through the hurdle in his heart. He always thought that his sister's death was related to himself, so he didn't escape until the end, but chose death.
In fact, this drama mainly conveys a spirit of great love, a spirit of selfless dedication and sacrifice of the ego. Although it fell smoothly, this spirit has always remained in our hearts.