Wow. She heard what he said, saw his reaction to realizing she heard it (and we've been told his emotions show very clearly on his face), and then thought about it for a while before deciding to invite him over late at night despite her apparently notable past of rejecting many colleagues.
Putting the romance aside, I'm wondering what her past is like. She's lived in a small apartment by herself since high school and we've just been shown that she lied about her previous social activities. She's also confessed having a lot of uncertainty and lacking confidence despite her outward impression. What skeletons lie in her closet?
Edit: I just binged the entire thing over the past hour and a half. I wish the slice of life arc could have lasted a bit longer, although that's a tough sell in the online serialization market. As of right now, Esther has gotten a lot more development, backstory, and personal connection with the main character, even if he doesn't have the hots for her and she doesn't think of him that way yet unlike the female lead. I suppose once Joy gets that same sort of attention, that may flip.