I'm pretty sure his dad didn't kill jin's parents but only blames himself for it. I don't understand how he would know that his mom was an oni if she herself didn't know. he only could've known for sure after death since oni's horns appear for a second post mortem.
I predict this is a sasuke -...
i think hongo has feelings for yuushin, since he swings the other way he doesn't feel embarassed or shameless sharing a house with a girl alone. that's what i got from miyu's reaction and that flashback