It wasn't explained well in the novel but when she astral projected, she got blonde hair and green eyes. I'm not sure if it's because the translator omitted that part but Tarkan sort of just breezed over the whole "yeah it was you all along and lost your memories of me." and proceeded to actually destroy a bed by making babies with Aristine so hard. Lol.
He will become an ally for Aristine (mind you, to Aristine only). He will genuinely fall for her. However, on the recent chapters (the one I'm reading is currently ongoing translations), somethings will happen that readers speculate whether he or the Queen was behind the threat to Tarkan's life to take Aristine. He was more like passive at first but recently decided to became active to fight Tarkan (whether to fight him for the throne or for Aristine or both is up for discussion).

Am I the only one a bit worried that the flashback for tarkan’s first love had blonde hair? Like the only important character I remember that had blonde hair(that isn’t related to ml) is mc’s sister.
I’m hoping that if mc isn’t the first love girl(and he just remembered the hair color wrong) then hope the first love girl never comes in or had like a tragic backstory where she died and that’s why he can’t get over her or some sht.