Question: What is the relationship between Ayato's 'mother' and Haruka? I think they should be cousins, except for the fact that Haruka refers to her as Oba-sama - which may indicate her aunt.
How far into the series have you seen? How much you know about their relationship depends on how far you've seen...I wouldn't want to spoil things prematurely...
But I can say some things which aren't spoilers. First off, 'oba-sama' can refer to any middle-aged woman who you personally know, not just an aunt. Thus, Haruka knows Maya personally, but is not necessarily related to her.
You say you think they should be cousins
I've seen the whole series. Maya seems to know who Haruka is, and it might also be the case that Haruka knows Maya, as she announced her name to her. She probably didn't know him as Ayato's mom.
I'm far from an expert in Japanese honorifics, but I think 'Oba-san' would be more appropriate to use for an unfamiliar person than
r t h a n t
Haruka and Maya knew each other very well. When Haruka and Ayato were 14, Haruka saw Maya a lot (as Ayato's mom, of course). She didn't know Maya was Dr. Rikudo's 'daughter', of course, although it's likely she knew they had worked together.
Haruka and Maya are NOT blood related. Maya is a mulian who was adopted by Dr. Rikudo. Haruka is a human who is Dr. Rikudo's niece.
Maya has genuine affection for Haruka, although Haruka's relationship with Ayato interfered with her plans. Maya attempted to erase Ayato's memories of Haruka, which is mostly successful. Nevertheless, when Ayato again chooses Haruka over Maya, Maya doesn't seem very upset at this.
There are a few times in the series where the most plausible explanation for Haruka escaping is that Maya let her go. In particular, when she refuses to order any attack on the escaping Vermillion, it's difficult to interpret her actions any other way.
Yes, that's correct.