Why did Cui Cui, a border town, suddenly cry when he sat by the stream and looked at everything under the twilight lock?

Cui Cui's parents died, and she was lonely. Although loved by grandpa, how does grandpa understand the girl's inner worries? No one around can understand her, so she feels that "life has become a painful thing." The boundless and hazy water surface made Cui Cui feel confused and helpless. She seems to feel the sadness and fate of ignorance in the future. ...