Man, Hajime really needs to figure this shit out.
It's obvious from the way Yue behaves that she knows there's going to be at least two or three others, and that she is (mostly) accepting of that fact... just so long as she is the First and Foremost Girl and eveyone else abides by the pecking order. But our man has to be so chuuni about how he portrays himself that he hardly ever considers the issue. Instead, he just carries on in the hope that everything will magically work itself out by the time he gets back to Japan. Or rather, he's lying to himself that it's not something he needs to worry about.
I wish he'd realize that, no matter how forceful the other girls are being about the matter, that he needs to sort this out. And it'd go a long way towards that goal if he sits down with Yue first and gets her honest opinion about the matter.