edit: digging into past posts, this looked like the same event as in post #787395 (same onsen), but Sanae was absent from that one, so it is not despite the similarities.
Brauny74 said: Yukari has a breasts. So she's female. And I think, Yakumos really represent a friendly family - Ran's husband, Yukari's - wife, and Chen's - child.
Chen does look like their child, 3rd pannel is too cute.
Anyways, I has been wondering if the Kogasa doesn´t have children of his own? Someone mentioned in a comment he´s in his fourties, I think. But knowing how workaholic both can get...
I blame Japan´s low birth rate (which in part is due to people working 24/7). Of course, I´m supposing that Kogasa is actually male.
Kogasa-shan♡Because it's snowing today, the scenery will be amazing.♡Tōbu Isesaki Line, Asakusa StationTime to get off.How We Appear SometimesOh, they're here.I am looking forward to eating bento while riding the train.What?! But I haven't eaten my bento yet!!Tōbu Nikkō Station