How can they date when no one has asked the other? I mean, it feels like they are on the verge of popping the question, sure. But you can't date unless you ask...or that's how I think it works...has it changed since I last had a gf?
In ch04 Tsukushi asked Hinoka to tell her she loved her. Wich she did. Now, Tsukushi didn't intend for that to have romantic undertones at the time, however the way in wich Hinoka told her she loved her combined with some of her comments on subsequent chapters (in ch05, when Tsukushi accidentally touches her but while trying to take her hand, Hinoka only asks that she tell her beforehand next time, so that she may be mentally prepared. And when Tsukushi later asks to touch her boobs she refuses because "I'm not ready to move that fast".) have made some of us believe that Hinoka thinks that they are already dating.
I mean, it's probably not it. But it's funny to think about it in that way.