被淋湿的诺言淹没在心里
[bèi lín shī de nuò yán yān méi zài xīn lĭ]
This implies a broken promise. The 'rain-soaked vow' means that once a promise is made but eventually betrayed, it's deeply submerged within oneself like waterlogged promises drowned by rains inside one's heart, symbolizing unfulfilled hopes and sadness hidden in mind.