人去楼空u
[rén qù lóu kōng u]
The term 'empty building after people left' refers to an empty house/building where the people who once inhabited it have gone, leaving behind a feeling of emptiness. It can represent abandonment or loss. Adding 'u' at the end might personalize this statement towards someone specifically – implying a sense of personal desolation and nostalgia, directed perhaps at the one who has left.