Nuh...if you back read all of the comments you'll know why.
For example and straightforward Dahye was attentive than Joy when they date with Yuna. It's quite ideal for that move when Dahye being in safe mode with Yuna than confrontation which she is afraid that Yuna is straight. Because how Yuna easily flustered with a man than woman to be exact. And for that which I want to clarify how Dahye formulate her imagination was when her brother and Yuna interaction. Which you may know that Dahye didn't know that her brother is gay.
In a perspective of someone you knew and being like that for your brother you'll be having a guessing game too like Dahye.
If you know, Dahye was like dating men because after all its for Yuna and not for her. The 5 chapters gave it away for the otp and how Dahye treasured Yuna. Because Dahye introduce Yuna as more than friend which to be exact she reprimanded it to voice out for Yuna after that kiss.
Maybe I was wrong but that was my observation.
Someone was here and saying it's Dahye and Yuna is endgame than Joy. At first, I was with Joy than when I analyzed her with Yuna. She is like a prince charming but her way is off for me when communicating to Yuna. While Dahye is a typical character who is naive and afraid to be out of her comfort zone.

yall get so surprised who yuna chose at the end