Honestly, at this point, their body language is almost that of a couple. Just look how comfortable they are with touching each other and being physically close - Like the scene where he casually took her hand, led her to the roof, and stood right behind her back with his hands around her, like it was a normal and obvious thing to do.
I love that from the very beginning they don't make a big deal out of small situations like that. Those moments are not the main focus, but at the same time, they do show us how their relationship develops. It might be the first ever romance manga I've read that does this so well.