FL's soul transmigrated to Giselle's body after the og Giselle did a black magic to summon a demon. Og Giselle did that to have revenge on Vivian (ogfl).
However, the twist is the one who taught Og Giselle how to summon a demon was actually Viviana, Dillan(ogml)'s master.
Ya the person in Viviana's body is bad because when she was little her master did black magic on her soul and switched her soul with another student of his. And that student is vivana's actual mother Charlotte. So right now who we are thinking that is Vivana is actually Charlotte's soul in viv's body (Charlotte is viv's real mom)
The main villian is Charlotte aka Vivian and the old master
If you have any other questions ask me.
I messed up the names my bad (remember this for later, og ml, og fl and ml have the same master) the master's name was berryfin or smth, and he was called the "archmage of white magic" or whatever, when ml stole all his magic he almost were to die but then vivana/Charlotte came and healed him, so he in the end becomes just a normal human and vivana and dillian were hiding that he was alive. The master uses his blood to control people he can control tarantulas to spy on fl or poison her. To answer your question, I think that's just for a plot point they don't touch on it (it has been a while since I read the original novel, so I'm not really sure. If I do find anything though I will reply to you)
Actual spoilers:
Her hair is changing because her Korean soul is settling into this world.
Ml's hair turns silver when he uses too much mana because of his broken vessel.
Our mc's name is Lee Yoosil, she doesn't reveal it to our ml until the side stories.
In the end of the novel after the big fight our mc forgets her part of Giselle and her time in the new world and basically just remembers that she has been reincarnated. By then our ml's hair is completely sliver and then he changes it back to black. She ends up remembering everything and feels bad she forgot.
Ml.
He developed magic at 8 it was black magic and his parents got him reported to the authorities to have him killed.
He got saved by an archmage and there he met og fl and og ml.
His identity as Wayne or the final villian gets exposed pretty early on, and when that happens he tells fl his past.
Og fl
She pitied ml and wanted to purify him because of his black hair since she saw him as a best friend. She didn't know that what she was doing (purifying him) was actually hurting him, she was just listening to her teacher. She has this thing where she can consume other mana and that's why she was consuming ogml's mana. Also she dies at the end.
Og ml
Idk he ain't important but he does kind of redeem himself.
Isabelle (cursed doll)
Her soul was a human one before and she now communicates with our fl and tells her information and teaches her most things about magic.
PLOT TWISTS?!?!??!
Og Giselle was taught by dillian og ml's master (vivan) how to summon a demon. And the plot twist greatest of them all is that our fl's soul is actually from this world (the novel world) and somehow ended up in the modern world and her actuall sould is vivana whose body is stolen by Charlotte.
Also later in the story dilian gets interested In our fl and he snaps out of his hypnotize and shit with the help of the villian doctor.
Relationships:
Also dillian was HELLA HELLA interested in our fl but she didn't give him a damn you could almost consider him a 2 ml.
Even after she learned that she's viviana she couldn't handle the thought of being a self righteous shit.
Also our ml went cray cray about fl and locked her in his mansion like 2 or 3 times also when fl told him about the novel he was like "yeah, that novel"
Also when he later learnt that our fl could have ended up in Vivana's body and probably ended up with dillian he went psycho. And ofc she handled him, (no he didn't go on a killing spree.)
Also og fl is dead
I can write more but the self satisfaction isn't enough for me, nor are the thumbs up I will get. (I'm lazy, maybe will write more in the replies later [maybe])