The novel is truly terrifying, but I believe the drama will be different. In the novel, they never got married and he didn't know he had a child, while in the drama they will get married and he will meet his son, which is already a big difference.
Completely heartbreaking. FL suffers too much and dies in the end, ML marries someone else, and years later kills his own son without knowing who he was.
(I don't speak English, I'm using a translator, I hope it's understandable)
I'm still unsure if these are alternate or continuous endings. Because exactly at minute 31:23 of episode 40, after Duan Xu passes through the light, He Simu appears straining her hands, as if she's trying to use her powers but can't, and the extra scene takes place right before that. If you combine both endings, it seems to me that at the end of the drama she had already turned human and was just waiting for him to return, and then it's completed with the ending of the extra scene, where they finally reunite. Does this theory make sense?
Estou até agora na duvida se são finais alternativos ou contínuos. Porque exatamente no minuto 31:23 do episódio 40, depois que o Duan Xu passa pela luz, aparece a He Simu forçando as mãos, como se estivesse tentando usar os poderes mas sem conseguir, e o extra se passa exatamente antes disso. Se juntar ambos os finais, pra mim deu a entender que no final do drama ela já tinha virado humana e estava só esperando ele voltar, e aí completa com o final do extra, onde eles finalmente se reencontram. Essa teoria faz sentido?
K-Drama 
Who thinks YPJ will lose his memories?🙋🏻♀️
Who thinks he won't?
(I don't speak English, I'm using a translator, I hope it's understandable)
https://m.youtube.com/shorts/JH_-2rnnpkQ?ra=m