悄然离去蓦然回首
[qiăo rán lí qù mò rán huí shŏu]
This online name expresses a bittersweet feeling. 'Qiao Ran Li Qu Mo Ran Hui Tou' means to quietly leave but suddenly look back again, indicating a sense of regret or nostalgia. It reflects the moments when someone is leaving and can't help but turn back for a last look.