Responses

No, it looks like everything was arranged by Norihiko. You didn't read the chapter where it talked about his life and motivations? He likes breaking people down, of course. But the father and mother are to blame for making OTHER people suffer. Norihiko is NOT responsible for that. Thanks.
Ranzo and Ikuro are childs that is made a victim because of fhe greediness of the adult around them. From the very beginning they were deprived of a normal family that there can be.
Ikuro is made to hate Ranzo for being a neglected child by his unstable mother and immoral father.
Ranzo was made into a sex slave by his own father (just how disgusting is that) and was hated by his step-mother for shit reasons that can not even be associated to him. It is the father's fault for looking his ex-wife in his son and causing his nee wife to be unstable and being jealous beyond rationality towards Ranzo. Like fudge, instead of being a crazy woman, help the child instead to be freed from all those madness! but then the nature of the family they belong to is also a root of the problem. They are from the rich and influential family where envy, betrayal, greed etc is as good as their future (well in this kind of setting as always).
And lastly, Norihiko may also be a victim of the vicious effect of that family. He may be made to be twisted with all his ambitions, envy, failure, regrets that is also to be rooted in the yeah family/house again.
Anyway, they have come to be all twisted because of maybe one reason... well who knows hahaha can it be the father wherr as of the moment seems like to be the root of all these? or was the father also a victim of something? too much love turned to obsession to his wife? stress and pressure from the business and keeping the house' influence? well i'll stop now here hahaha