I make an exception for Momiji and take her fanon into account, since it's actually pretty much in line with what we know about her as a character. Except for the "liking Aya" thing. :V
She has an overly serious attitude and enjoys gentlemanly board games such as Shogi, suggesting a samurai-like attitude, which is kind of funny because it clashes with her cute, fluffy appearance. She seems to have a few dog-like features, since she's very loyal and apparently she literally bites people?? Samurai doggy girl easily qualifies for moe in my book.