There's one possibly-relevant translation issue (Japanese -> English, nothing to do with JSL) in the pages @nhahtdh posted that might be confusing people's interpretations of the scene. On Page "-5", Ishida's last line is more like "Not being able to hear your voice made my life difficult." - he's talking about himself, not sympathizing with Nishimiya. On what would be page "-4", he goes onto say that things would've gone better if each of them could hear what the other had to say.
Contra @ssh's answer, there's no reason to suspect that Ishida blushing had anything to do with Nishimiya showing him something on a piece of paper - she'd only just gotten her notebook back from Ishida after 5 years, and we don't see her writing on it.
Why did the boy blush and reply "That's so embarrassing! How can you even say that?!" in page second to last?
Here, Ishida is referring to the scene around pages 26-27 where Nishimiya signs to him "you-me-friend" / "can you and I be friends?". This is a very touchy-feely and generally non-boyish thing to say, which is why Ishida expresses that it would be "so embarrassing" to say something like that (especially given his treatment of her prior).
And in the last page, when the girl grabbed his hand, why did he say "That's not what I meant!"?
As we saw on page "-3", clasping hands indicates "friend" (or, per the text given there, maybe something like "become friends"). By taking Ishida's hand, Nishimiya reaffirmed that she still would, in fact, like to be friends with him. I imagine that Ishida's startled reaction there indicates that he viewed their meeting not as a chance to make up with her and start over, but more of a chance to say "hey, I'm kind-of-but-not-really sorry about what happened back then" - he wasn't expecting Nishimiya to be so congenial to him, I guess.