i think so too actually in my own comprehension about this was the mother really did rape in addition of violence to him. and for satoru's shock he just beat the crap out of tha bitch thats why he ended up in jail. or its just my imagination working LoL.
@shou, I saw that too, so it's not imagination. XD
it is like that the mother was raping him for real that why the younger twin beat his mother
Just going to point out that in the panel where Satoru caught his mom beating Tooru, you could see the nipples of her breasts. It might just be me, but I think the mom was raping him? I kind of got confused. Ahh, but Satoru and Tooru are adorable together~