From what I understand as far as the story goes, Yen has a crush since high school on Dae's friend (blonde with bf) from high school. The mystery as to why blonde doesnt know Yen where in fact they have a common friend (Dae) is what makes it intriguing.
Ooohhh it's finally here.
I second this and my guess is maybe Yen knew about her crush through Dae but is shy to approach her crush because they're both girls, parents dont approve or something? I'm hoping there's a deeper backstory to this especially if the setting is them being in college already.