Bulgasal becomes more interesting from epi 2
After ML turns into bulgasal former FL takes his soul & turns into human (now she will born with his soul in every birth) and he becomes soul less after that royal army orders to kill him but they unable to do so in a meantime his adoptive father tries to save him but one of the army soldier kills him
After that ML promises his adoptive father that he will not feed off human's blood but rather he will feed off animal blood for his survival (bulgasal feed off human blood just like vampires)
Then in 1597 he was searching for reincarnated FL by her drawing & one man told him that he had seen similar painting in one cave.... ML goes to that cave where one weird looking oldie tells him that he killed that women after sometime it is revealed that oldie is none other than reincarnation of dueoksini (monster) who is after ML's soul.... ML kills him and tells him that if he again tries to kill FL in next birth then he will kill him in his next birth also
Now show jumps directly into 2006 where they had shown that ML is still searching for FL by 2 photos (one is teen version nd one is adult version photo) .... Here one side it is shown that FL have one identical twin sis who is chased by some men .... When FL sang yeon gets to know abt it she runs away from home with her twin sis sang un (she still remembers her past evn after reincarnation)
Then they goes to one strange lady's home who is FL sis from past life & then she took promise from her twin sis that she will never call or tries to contact her mom & 1 younger sis otherwise they will also die but in midnight FL's twin sis calls her mom nd then her mom takes her from airport nd when they reaches home at a time FL also comes and says that run away from her otherwise bulgasal will kill them
But they cant run away from home as bulgasal is right next to their door so FL hides her sis in cupboard and bulgasal kills FL sang yeon & her mom .... Somehow FL's twin sis gets saved nd then she takes her younger sis with her and goes to same lady who is past life sis of FL
Now show again took leap of 15 yrs now new FL is sang un who is Main FL's twin identical sis .... Main FL took promise from her sis that she will kill bulgasal by special sword
(Here one thing is still not confirmed that who killed main FL in her modern era reincarnation .... I think dueoksini monster new reincarnation killed her not bulgasal bcz bulgasal is still searching her for his revenge) .... Here main villain is clearly dueoksini monster
And btw bulgasal is itself never ending curse and its repetitive cycle.... Its like when FL takes revenge ML turns into bulgasal nd when ML takes revenge FL turns into bulgasal .... Bulgasal is immortal so it cant be killed nd it only transfers from ML to FL & viceversa
Edited : I think this both the twin sisters are reincarnation of same person (Main FL) while one sis remembers her past and other doesnt
The other twin sis must have soul of main ML which he wants to take back whereas first twin sis killed by main villain
