Why can't I understand the second part of the movie "Unspeakable Secrets"?

Finally, Xiang Lun found that Xiaoyu and he were not of the same age, and they were 20 years apart. Xiaoyu is also a student of Xiang Lun's father. When I was studying in Xiaoyu, one day, I suddenly found a piece of music under the piano in the music classroom. The name of that music score is Secret, and it also says that if you play this piano piece quickly, the first person you see is the person you like in the future. Things in that classroom have been moving when the light rain is released again. Unconsciously, she came to this classroom 20 years later. At the first sight, I saw Xiang Lun who was attracted by music. Because there is another girl in Xianglun's class who likes Xianglun. But only Shannon can see the light rain. One night, Xiang Lun made an appointment with Xiaoyu to meet in the piano room, but Qingyi arrived first. Sharon closed her eyes and thought it was a light rain, so she motioned for her to kiss him. It's a pity that Xiaoyu happened to see it at this time. She thought it was Xianglun who moved on. I didn't go to school for a few days in a rage. Xianglun has been looking for Xiaoyu for a long time. In fact, Xiaoyu came to the music classroom. I played the song "Secret", and now the time has gone back to 20 years ago. Xiaoyu told Xianglun's father about it, and everyone thought Xiaoyu was crazy. Xiaoyu's mother also specially bought Xiaoyu a medicine for treating mental illness. She was laughed at by her classmates at school. A classmate wrote a note to Xiaoyu during class and asked her if she lost her virginity after 20 years. Xiaoyu is very sad. After returning home, I will never go to school again. When Xiang Lun and Xiao Yu were together, they once said to Xiao Yu, "I want to play a tune specially for you at the graduation ceremony". When Xiaoyu graduated, Xianglun's father came to Xiaoyu's house to find Xiaoyu, hoping that she could attend the graduation ceremony. Xiaoyu remembered what Xianglun had said. After taking a photo with Xianglun's father, I went to the piano classroom again. She played the secret again, and 20 years later she came to Shannon's graduation ceremony. I heard the Swan played by Xiang Lun for her. Just then, Xiang Lun found Xiao Yu, who had been looking for her for five months. Xiaoyu saw Xianglun looking at her and ran away at once. Xianglun ran out to chase Xiaoyu before playing the piano. Sharon hugged her when she caught up with her. Say to her, "promise me you won't disappear again." Xianglun's father chased him out and scolded him for letting him continue playing. Xiang Lun turned and let Xiaoyu wait for him in the classroom. Turning around, unfortunately, Xiaoyu saw the lucky bracelet that Qingyi lent to Shannon. Xiaoyu thought that Xianglun had been lying to her, and returned to 20 years later. After the graduation ceremony, Xiang Lun came to the classroom. I only saw his two friends stealing from others. Xianglun asked them if they had seen the light rain. They're weird. Xiang Lun went on to say, "That's the girl who danced with me at the dance again". They were all surprised. "At the ball, you were dancing alone." Xianglun remembered the dance that day, and the girls all said to him, "If you don't have a partner next time, you can come to me." It's really strange to think of Xiaoyu again-why doesn't she have any friends and nobody cares about her, and the school piano room forbids her to play the song "Secret"? Xiang Lun was puzzled and went to Xiaoyu's house again. I saw a picture of Xiaoyu and his father. And secrets. After uncovering the secret, Xiang Lun and Xiao Yu's mother saw it. Xiaoyu painted Xianglun 20 years ago. Xiaoyu's mother just found out that she was wrong about Xiaoyu. He was suddenly very sad. When Shannon got home, she talked to her father about Xiaoyu. Xiang Lun's father said. Xiaoyu was his student 20 years ago. You play the piano very well. Just a little paranoid. He also said that he liked a boy after 20 years. They all think Xiaoyu is crazy. It dawned on Lun Qian and immediately ran to the school music classroom. After he went, he found that many people were tearing down the house, and it was too late to see the time. He climbed in through the window and played the song "Secret" as quickly as possible. At home, Xiang Lun's father saw the music score of "Secret" left by Xiaoyu, and found that Xiaoyu wrote the words "I love you" on the back of the music score 20 years ago, with the signature "Lu Xiaoyu". Xiang Lun's father opened the folded corner in the upper left corner and saw the words "Ye Xianglun". Only then did I know that Xiaoyu loved her son. He ran to school as fast as he could. At the same time, Xiang Lun has played the last paragraph and finally came to the world of light rain 20 years ago ... However, Xiang Lun never returned to real life, so he did not really appear like Xiao Yu, but really appeared 20 years ago, and wrote another touching movement with Xiao Yu. ...