^How can you question who is the real mother? XD Anyway, I don't really want to know.
It's interesting how Izumo turns to Yukio. xD And in volume 15's special chapter she was hiding behind him too. It's like he's her safe guy or something.
I have been thinking about this and... I actually wouldn't be mad at all, even though I ship RinIzu since the bathroom incident, if the ending was a reverse ship of Yukio x Izumo and Rin x Shiemi.
A safe guy is usually not a love interest. It's a guy that for some reason she believes would never harm her and would never try to make advances to her. The reason can be that, in addition to being a nice guy, they're family or he's already married or he's her teacher or her boss or they've known each other for a long time and nothing never happened or he's gay...
Usually girls use safe guys to chase other guys away or they use them to do things they're too shy to ask other guys.
Like, girl:"I need Joe to give me the keys of the lab, but he's in the boy's locker room right now, can you go and ask him for me?" guy:"And you came all the way to the library to ask me? :/ "