i think the plot twist is that giyoon was acting like he didn’t know there were two Yitaes (the ghost one and the human one) but don’t quote me on this cause i’m taking this out my ass by following the context clues lol
It looks like GiYoon pretends he can't see ghosts, so he pretends that the ghost is really Gitae and this ghost took on Gitae's form because he thinks that tis GiYoon's preference. Just now the ghost Gitae found out that when the director kissed him GiYoon didn't run away, but when the ghost tried to kiss him he ran away. That's when he realized the discrepancy. And accused GiYoon of having pretended.
Wait what’s the plot twist supposed to be…? I feel like nothing can surprise me anymore since I’m so lost now LMAO