I can see why Heesoo/Haesoo wants answers, BUT to some extent all that feels like her looking for excuses to back off.
All the time, she's felt like she needs to disappear, and sort out her own shit, and that she's been interested in him to use him as a way to both treat herself, and to distract herself from/cope with her own issues.
She should just tell him that she isn't truly interested (if she really were, she should have acted on that a LONG time ago), so he can lift his eyes, and see that he
a) can sort out whatever he and Mia have/had
b) can actually have someone functional who's been there the ENTIRE TIME - Hayoon ...
And yes, I'm guessing this will all end up with Mia.
Or we get some ridiculous bad end ...