旧城旧爱不复存在
[jiù chéng jiù ài bù fù cún zài]
It refers to an old love or affection from the past that no longer exists in the former city (representing old times, familiar places, or memories of people who once loved each other), signifying a farewell to the past. This kind of username is often used by people reminiscing on old times with a bit of nostalgia and melancholy.