I actually think the missing dad is a running gag.

I'm strongly suspecting Obata was getting a little bored of drawing the ordinary world of HnG. Hence the interesting illustrations.

I have also noticed that Sai was not shown in scenes he was at. Maybe because he had nothing to say. At the moment he can't really help Hikaru any more; he's taught him all he had to teach. So that leaves Sai's angsting thoughts of the future he hasn't got, and they've put as much as they could in without over doing it.

'Poor Waya' my grandmother. That boy can take a bit of wheeling, he's good enough at dishing it out. All in fun of course!