I know this is a manga about relationships and all, and maybe this doesn't really interest the author in terms of how he wants to tell the story, but this is a legit question:
Have they had sex? 
I mean, they live together right and all that sleeping beside each other stuff, 
but I haven't read a chapter that they've done anything more than kissing. 
They've probably done it knowing the culture, but I just wanted to point out that this is kinda a first for me 
where a relationship manga where 2 people living together don't talk about sex at all
Anyway, don't mind this pointless rant to a very wholesome manga