i really didnt see it coming, i mean all of the corpses looked horribly messed up, made me think that he was a total nuts because of the suicide of his mother. but the author show us this chapter, and it makes even more sense to all of his doing. his reason and his suffering. i bet he thought that it would be better for the family if their relative murdered in such a way rather than died by taking his own life. but still he;s a psycho for sure.
i'd like to see what;s coming next. it was already good even before this, but its gotten more interesting from this point.
edit:
now that i think about it more that it was really something when the friend of mc, the one who had sex while cleaning stuff, died mutilated. he was really in a bad shape at that time, and he decided to visit his old house. and if, just if, he actually intended to take his life for sure at that time. then what the police believe masato to be is true, and it makes things even deeper, it makes me imagining things and all of them are really depressing.