When he made up his mind to be with her, he went over to the Yangs and broke up the marriage agreement. He then chose to enter a university in the city she was at, but… he was afraid that the fact he once had a fiancée would become a point of conflict in their relationship. Worried that should the marriage agreement be exposed, she would blame and fault him for it, he even took a precautionary measure.
When he agreed to be with her, he emphasized, "If one day you were to find out that I've hidden something extremely important from you, you must definitely not get angry at me. That's because, I'll only be with you!"
However, despite his careful hiding of the fact just because he was afraid of her being hurt from the truth, her very most initial motive of being together with him was exactly a method she was using to get back at Yang Sitong!
How tragic was that?
He had not noticed that at all when they were together.