I have no idea why some people say down the road that they can't feel the chemistry between the two. They've been slowly building feeling for each other for a while now, and have been constantly supporting and being there for each other. To those who say they can't feel it, they don't understand what relationship really is like if they're just leaving it up to some "feeling."
Yeah... I was seeing the first proper inklings back in the sixth chapter (third episode of the anime, second half), where he follows her out of the house (albeit at the behest of grandpa), and then just... keeps her company while she cries as much as she needs to. It's a simple thing, but it can mean a lot to someone hurting.
Seriously, just... pretty much every time they're alone together, there's growth between them (and a few when they aren't quite alone, too). If people can't see that, yeah, they don't know what it's really like. Hell... the way he ran off to find her in Kyoto, that reminded me of a number of moments in my relationship with my ex, both when we were just friends and also once we were more than that. Running off to help someone you know must be, or definitely is, hurting, and then just... spending time with them. He does this quite a few times for her, in fact. And every time, their bond grew stronger.
Those moments really speak to me, as someone who has loved, and lost. Not every romance needs grand moments- simple moments like these cannot be understated. It's why I fell in love with this story, and also why I really enjoyed Saekano, as well... though the sharp tongues of the girls were real fun, too. Great comedy in that series. But the romance in that was made up of really simple things that just added up, similar to this.
Also remembering how much I really enjoyed Namaiki Zakari, but that was just so full of amazing moments of relationship growth I struggle to really quantify it. So much feels, as they say.