I think we saw her have a flashback with a guy wearing some really old traditional clothing. I really wanted to hope she was in a coma too, (bring it on ghosts kdrama ending) but I think she’s been dead for centuries now. Maybe that’s why she’s so powerful? Unfortunately, I don’t think there’s a happy ending where they both get to live as humans together.
& that's why i said she might have mixed up her memories of past lives & present lives. I also can only hope that the author gives our taerin a happy ending
my take is thar they’re soul bonded.they used to be lovers back when serin was alive and he too ,He reincarnated she did not.We dont know why yet but this might get a happy ending in a sense.Like serin finds what makes her stuck as a ghost she transcends gets into the cycle of reincarnation, he dies they meet again and voila .every lifetime typa shit (ノ≧∇≦)ノ
I have a feeling that serin is just a normal girl who happens to be in coma for a long time in the real world & her soul is just floating around rn. But her past lives memories & this lives memories might have gotten mixed up & she also forgot some of her memories of the real world which might be the case. Again it's just my assumptions (〜￣△￣)〜