While Chang was about to say goodbye to his memory, he took out a pack of cigarettes from a drawer in the bar counter. Qing Shui gifted the pack to him, but he'd never learned how to smoke, even after four years. The act of lifting the cigarette was more of a habit than smoking itself.
Chang only did it when he felt unhappy. The smoke swirled up in the air, twisting, hovering. It was nostalgia that he was smoking, not nicotine.
The smoke reminded him of a slang that people used online back in the day - "floating clouds."
He wished everything that happened and would happen were just floating clouds that eventually went away; he wished that all of this was just a dream that he could wake up from so he could have his carefree life back; he wished the only thing that he needed to worry about was the reading that he never finished and the pretty girl beside some louts.
An explanation for Yin Qing's name:
Yin means music, melody. Qing as a surname is rare, meaning a state of lucid mind or simply pure.