我配不上你我独你唯一
[wŏ pèi bù shàng nĭ wŏ dú nĭ wéi yī]
Roughly translating to 'I do not deserve you; I am unique only to you'. This implies a self-deprecatory statement, feeling unworthy in the face of someone's goodness. And it may mean even so, the one bearing this username believes themselves to be irreplaceable in this specific person's eyes.