Yeah it was crazy how Shizuka gives Naoki Azuma the lovey dovey eyes and suddenly he agrees to become an accessory to murder. Then again he is just a kid and doesn't really understand the full scope of what he has done. That being said, I suspect that Shizuka learned how to manipulate by watching her mom manipulate her male clients. Also I think Marina's mom says she's "not my daughter" simply because Tapoka sided with Marina's dad in that moment. Of which in the past Marina would of probably rejected the offer by her dad simply to please her mom and be seen as being loyal to her.