Hm... according to my calculations the only ways we could have a childhood friend Heroine is either if she always had her eyes closed /averted her eyes in front of Rentarou or...if she wasn't a girl during their childhood. Extreme tomboy could also work for that.
Oh nice! I mean their newlyweds who can still conceive and their pretty passionate about each other. So it was only a matter of time. As I say, sex doesn't have to happen on screen once a relationship vis established. Take, Clannad for instance.