Yeah, me too.
I'm actually reading everything again, so I can tag and keep track thru mangago.
Even though sensei work being so twisted, so dark I love it. I think that is very feral, it’s an addiction. Like when people say that someone / something make you lose yourself and you become something else, you became dependent of that situation, of that thing, of that person.
The manga is twisted, but I'd gladly read a lot more stories about the relationship of this father and son.
I read it a long time ago, and Ogawa Chise is one of my favorite Yaoi mangaka. She's have so much dark in her manga, and this one prove it. May think the father can't even live without his son anymore, because just his son can relieve his anger, just like drugs. Without it, you'll die slowly...