Rine's sister is blonde BUT she lived in silver spoon ..from the flashback the lil girl just wore simple cheap white-ish dress .. I don't think such a glamorous second princess would wore such a shabby dress.
So this is my theory, I think the girl is Rine..why ? Cze she have an eyes that could see future and past . She have a strong longing for fatherly love to the point she always saw the interaction between his father and his sister.. maybe in her mind when she was a child , " maybe if I have blonde hair and act like lil sister, I would be love by our father too?"
I think maybe she dye her hair blonde ( I have no idea how she get her access on the dyed)
On another context maybe Rine and Tarkan do met when they were children, and the one Tarkan met and fall in luv with was actually Rine that actually have a similar hair with her sister at that time ....I bet the father would dislike it more and of course Rine would need to get rid of the blonde hair for sure.
I hope if this was the case , Tarkan wouldn't think that he actually like the second princess when he met her in the future (⊙…⊙ )
Sorry I typed too long ⁄(⁄ ⁄·⁄ω⁄·⁄ ⁄)⁄
From the flashbacks, is Tarkan’s first love Rine’s sister?