Kohina calls herself a doll because she has no more emotions
She was probably abandoned by her parents
Inugami's behaviour is legitimate if you consider how inugamis are made: You have to bury a dog up till its head and leave a bowl of food or water barely out of reach and then decapitate it when it's about to die of starvation (Apparently they showed a decapitated head of a dog; Don't remember)
The lawyer in the last episode wasn't noticed by any girls and couldn't talk to his daughter because he was already dead (as you should already know), and the daughter was depressed as she was always alone (mother probably a workaholic as well)