I don't know why Rong Da can see the secret of Xiaoyu.

Twenty years ago, when Xiaoyu was chatting with Teacher Ye (that is, Ye Xianglun's father) on the playground, Xiaoyu told the whole story. At that time, young Dayong (that is, Rong Da in your topic) was sweeping the floor and heard it. At that time, Teacher Ye also said, "Dayong, you are too obvious to eavesdrop." Then Dayong smiled and said, "I'll go there to sweep." Later Xiaoyu was caught in class. Dayong has been sweeping the floor in this school for 20 years. Twenty years later, he saw a young light rain appear in the piano room. He knew it was played 20 years ago. After playing it 20 years ago, the first person who opened his eyes and saw it was the first person to see it. At seven o'clock that night, Xiaoyu came to Xiao Lun. He saw Dayong as soon as he went out, so only Dayong could see the light rain. Dayong also said, "I thought you were going to bounce back." Xiao Yu said, "No, I came to see Xiao Lun." Dayong said, "Sorry, you failed." This is because Dayong was the first person Xiao Yu saw, so Xiao Lun couldn't see Xiao Yu, which is why Xiao Lun drove it out of the piano room.