Has Hino ever smiled?
You're just trying to get me to re-read it again so I can pay attention to this aspect!
Went to do that myself... :D
Jokes aside, I think there were a few chapter-endings in which, naturally unbeknownst to Koguma, Hino did smile softly, even if just a tiny bit.
She's good at hiding even from the readers, often her reaction, especially when blushing, is mostly hidden by her hugging Koguma...
There are some very visible slight smiles in chapter 13, though, and a very lovely one in chapter 25 when they were trying to call each other by their first names. And following that, she spends almost all of chapter 26 smiling while chatting with Koguma on Line.
And that's as far as I bothered to check right now, should be enough.