"You were the hand he held on to during the most difficult time. But after he recovered, he let go."
Chen Guangyu thought he had "walked in" - because he accepted her when he was most vulnerable. That should be a sign of "trust."
But Lu Yangui only regarded those days as "needing someone to accompany him." Not "need her". Just "need someone".
It was only after she left that he realized that "needing someone" and "needing her" were two different things. It took him five years to figure it out. When the difference was clear, that person had changed his taste, changed a city, and changed to a person who would not wait for him.
Concept: Some love comes too early, and some knowledge comes late. She taught him love, and when he came back with his diploma, she was already at the next stop.