To be honest, at this point, this is Sato's fault.
The guy IS trying to close the gap and she keeps the cold act up, making other people think he's free to grab or soon to be single.
And Oshio isn't exactly the type to stand around, he's a sociable and nice person, he IS going to make new friends and acquaintances, some of which might fall for him, like that new girl Himeno.
The ball is in her court, she needs to overcome that bashfulness of hers and put her foot down. I suppose this arc is more focused on her getting her shit together, especially since the new girl is extremely aggressive unlike the one before. (nothing like a sense of urgency/formidable rival to make the main love interest realize what she's going to lose, classic lol)
EDIT: whoops "is in her court" not on