Zhou Xunian: An architect (or financial executive) with a gentle appearance and extremely stable mood. He seems to be gentle to everyone, but in fact he has a very high wall in his heart. All his "knowledge of propriety" were the shackles he personally put on himself when Shen Zhisui left.
Shen Zhisui: On the surface, he is an upstart/investor in the capital circle who is comfortable and unruly. He seems to not care about anything, but in fact he suffers from severe insomnia. He seemed to have given up, but every time he got drunk, he still shouted Zhou Xunian's name subconsciously.
It's not a bloody misunderstanding, but "I choose to be the bad guy for your future." When Shen Zhisui's family encountered major changes (such as bankruptcy and debt), in order not to hinder Zhou Xunian, who had excellent academic performance and was about to be admitted to a top university, he deliberately created an extremely hurtful quarrel, unilaterally cut off all contact, and went abroad to bear the storm alone.
Concept: "Longevity" refers to the long separation and growth, while "Echo" implies reunion. It means: I have called your name for a long time, and finally heard your reply at this moment of reunion.