He does come back to her the next day so she can clarify her answer to his confession and she refuses to answer. She said something along the lines of "figure it out yourselve". Too lazy to check the correct quote tho.
Took me a second to find exactly what you meant, but:
In chapter 1, she gets cornered by a group of guys who belittle Sorata (who's offscreen at the moment, trying to win a specific gacha pull that she'd failed to get) and try to pick her up. Sorata tries to confront them, but is weak and just gets knocked down. Miyuki grabs the guy and "aikidos" him and they all run off scared, and then Sorata confesses that he is not worthy of her, but that he intends to keep working hard to make her acknowledge him and starts/finishes by confessing that he still likes her.
And all she says is "thank you" while not meeting his eyes - which he takes as a rejection of his feelings for her, because in Kyoto the specific phrase she used can mean "thanks a lot", and outside of Kyoto it roughly translates to "don't bother me/mind your own business" (per the TL in chapter 2, page 3).
So in chapter 2 when Miyuki asks Sorata if he wants to have a study session, he expresses surprise because he thought he'd been rejected. When he asks for clarification ("By the way, what did you mean by, 'don't bother me' the other day...?"), and
Miyuki's depicted as looking panicked, then simply responds "why don't you figure it out yourself?" (ch2p4)
So yeah. Between Miyuki saying
nothing to the guys accosting her when they belittle Sorata to her face, and then saying
that to him when he tries to ask for clarification on what she'd said in response to his confession, it really does seem like Sorata's been putting in all the work,
in spite of everyone around him repeatedly saying he's not worthy of her, and Miyuki just never steps up to defend him, and she continuously runs away from actually being direct or even trying to make herself clear.
Which, is why I'm continuously surprised when people say this is solely Sorata's fault, throughout the whole thing. Yes, he's not perfect, but he's the one making actual efforts,
including trying to reach her and make their arranged engagement work as children in the first place over the course of years' worth of visits.