I think Jian was right all through till the point he had to murder her.
I couldn't just help but imagine what he would be going through right now.
Blazing hell!
He must have thought of her as redemption... He must have thought of a limited eternity with her. But he must have been blinded by love, if not he could have seen the red light a while ago.
He must have felt, killing her would justify his pain ND the fact that he was cheated by her (not love)
But moving on and learning from his mistakes could have been a great way.

To make matters worse, they both are people you know. I can't relate to the pain.