Young Runtu was one of the characters in Lu Xun's novel, Diary of a Madman. He was a rich, intelligent, witty young man with a similar character and experience to the protagonist Lu Xun. The story mainly talked about the childhood of Runtu and Lu Xun and their relationship. In the novel, Runtu was a child from the countryside who lived in the city with Lu Xun. Although they came from different places, as time passed, Runtu and Lu Xun gradually developed a deep friendship. Runtu was smart and witty, good at observation and thinking, and had a kind heart. He and Lu Xun had experienced many interesting things together, such as playing together, studying together, exploring together and so on. In the story, the relationship between Runtu and Lu Xun experienced many twists and turns. Runtu used to feel inferior because his family background was superior to Lu Xun's. However, as time passed, Runtu gradually understood his value and importance. He also began to pay attention to Lu Xun's life and experience and gave Lu Xun a lot of help and guidance in his studies. In the end, both Runtu and Lu Xun went through their own growth process. Runtu became an excellent scientist and made great contributions to human society. And Lu Xun became a great writer whose works influenced the development of modern Chinese literature.