What Nuwa suggested using the method of refining in the cauldron to gain Ye Fan's absolute trust actually meant Shen Yan had to completely give herself, becoming a true couple with Ye Fan.
Shen Yan harbored a sense of anger and resentment in her heart. She came to Ye Fan for revenge, though she couldn't even recall what kind of grudge it was. She just felt an endless grudge in her heart, wanting to kill Ye Fan. Driven by this resentment, she was unwilling to give herself, as if offering herself to an enemy but wanting to kill him was a difficult choice for Shen Yan.
