After Rong Yu ascended to immortality, he died together with the demon spirit and entered reincarnation again.
In the third life, after completely remembering the experiences of the first two lives, Rong Yu decided to change his strategy. He would no longer die with the demon spirit, but would live with him for mutual benefit. This breaks the curse of the endless cycle.
*
First life.
"You have a death pact with the devil. Only you can kill him."
"Okay. I'll do it."
*
Second life.
"You have become an immortal. It is the duty of an immortal to eradicate demon spirits. Only you can kill him."
"Okay. I'll do it."
*
The third life.
"Listen to me first! I am an immortal and you are a demon, but I don't want to kill you, I want to save you. Just let me help you!"
"Why should I believe you?"
"I'm the only one in the world who believes you won't do evil for evil's sake."
"... Let me think about it."
Concept: Life is a long-distance race, and it always has a similar rhyme.