Trying to a fanfiction.There was a Jungkook fanfiction I read on Wattpad. I think it's name was something along the line "Jungkook mature imagines 18+" (I could be wrong about the name). It had chapters like "Doll", "YN in Wonderland", "Doctor", "Blood Bank".
In the "Doll" chapter, Jungkook got a doll when he was a kid, he got so obsessed with the doll. He killed his mother for some reason and when he got older he turned the doll into a real living being. There's a scene in which they are playing hide and seek with Jungkook finding her with a knife and the doll (YN) trying to hide somewhere and he catches her (He has sex with her). Later they go to shopping and Jungkook gets mad at a lady for questioning him. He comes back home and starts doing black magic to kill the lady but he reincarnates his mother who kills him. That's how it ends.
In the "Doctor" chapter, the reader goes to Jungkook who is a doctor for a check up. I don't remember what problem YN had but Jungkook's thoughts are shown saying that she doesn't know she's pregnant, YN was married to someone else, and Jungkook had a lactation kink. YN's husband dies in a car crash after finding out about YN's and Jungkook's affair (not sure). At the end, YN and Jungkook are shown living together with the baby.
"YN in Wonderland " had YN somehow ending up in Jungkook's kingdom, Jungkook takes her Virginity for I'm not sure what but there was an agreement, I think it involved YN's father. Jungkook and YN end up falling in love but they are separated for some reason, maybe Jungkook going to war or smth, then YN is asked by someone to sacrifice herself for the kingdom, but when she goes there she finds Jungkook and they both live happily ever after. Jungkook and YN were hybrids in this one, I'm not sure but if you remember anything close to this please let me know
If anyone remembers or knows please reply with the author's profile.
