Legitimately, this is what happens with bullies like this. Their parents never believe them and they only face punishments from non-biased participants.
This manga is so realistic. So far I would have to say the only thing that has bothered me is that the author seems intent on humanizing Sako despite him r*ping Ayumu and blackmailing her about it. I wonder what will happen to him later on. Can't believe it's almost over!