He won't do anything because he'll probably come up with some tropey excuse like "I want to treasure you". In reality, he wants Hagiwara and the trope of he doesn't want to 'soil Hayami' is coming on hard. If he didn't know that Hagiwara wanted the D he would have been ALL UP ON THAT like he was at Christmas. The author has in effect, introduced a plot point that will see him reject Hayami's advances tonight.
Hayami (she read the raws?) wants to seal the deal. The unfortunate part is that anytime you pick somebody up on the rebound it's possible that they go back to the person that left them. I feel bad for this girl ... poor Hayami. Before he found out that Hagiwara liked him back I was all like 'seal the deal bruh' ... but as soon as the author pulled that stunt with the lesbian girl seeing Hagiwara kissing Hamaji I knew that they (Hayami and Hamaji) will NOT have sex. Even if they do seal the deal, he will still leave her to go back to Hagiwara. It kinda sucks but thems the breaks so to speak.