Well there are several possibilities
Maybe the brother and him are just friends
Or he is too stubborn to say he likes the brother and the brother flirts around to piss him off.
Or maybe the brother is a simple flirt whip dating him and nothing more than flirting
Or the Mangaka is laying the groundwork for a sequel with the two of them in the future.
!
Well, Nakatani-sensei said they'd "continue" after Inoue "became serious", so make of that what you will. Plus, Inoue came back and is now the athletic director for Nakatani's school, and they seem to be friends. There's a possibility their story has a Part 2.
I hope so
i think they got together !
look,it;s the same person after they've grown up ヾ(☆▽☆)
http://iweb9.mangapicgallery.com/r/newpiclink/after_i_win/6/56a58e318157bfebe8acf137fb96f177.jpeg
http://iweb9.mangapicgallery.com/r/newpiclink/after_i_win/3/0b8ae522d609d96452fef5a3e299963c.jpeg
http://www.mangago.zone/read-manga/after_i_win/mf/v01/c002/18/ Well if they did get together he's a fucking cheater. So maybe he's still trying to convince him? He better not be cheating.
Since Hiyori's story happened years after his big brother's story, I was wondering if those two are in an open relationship or are just friends. You can see during the first chapters that Nakatani-Sensei was doing a kind of threesome when his brother went to tell him to stay away from Kasumi. So, may be Nakatani and Inoue didn't become a couple and just stayed as friends? I definitely need more of them.