纯洁如黑纸
[chún jié rú hēi zhĭ]
'As Pure as Black Paper' is somewhat paradoxical because purity is traditionally associated with the color white, symbolizing innocence and untouched nature, while black paper seems like it’s been sullied and tainted. This may represent a sarcastic way of saying that the user has experienced hardships or seen the darkness in this world but still retains a kind heart beneath everything.