不知不觉爱上你后知后觉恋上你
[bù zhī bù jué ài shàng nĭ hòu zhī hòu jué liàn shàng nĭ]
Literally translates to falling in love unintentionally and only later realizing it. It expresses how love can form unconsciously and one only realizes it after the fact, often describing a deep but subtle affection that takes time to recognize.