For quite some time I've been trying to think of any K-dramas where a character, who was a lead's friend in the beginning of the show, becomes some sort of antagonist?
Most of the time it would be the opposite (say, two girls compete for a love of a boy, but eventually become friends). Or we would see an antagonist being a childhood friend, who turned arrogant or even became antagonist.
I am more interested in the shows where a character is actually a good friend/character in the beginning, and is sort of loveable, but writers eventually turn the character to a dark side.
Some references: True Beauty had this kind of character. If Naruto was a K-drama, Sasuke would also be this kind of character.
