I was the only one left on the last trip. I was sitting in a crowded carriage, but I felt particularly lonely. Sitting opposite a middle-aged couple, the wife has shoulder-length short hair, a simple but elegant casual dress, and always has a smile on her face. She took out a bunch of grapes from her bag, peeled them and ate them, and stuffed a few into her husband's mouth from time to time. At this moment, Fish Leong's "Breathing Pain" sounded on the radio, and she hummed softly. I listened, my eyes were moist, I didn't look out of the window, and my thoughts drifted back to four years ago.