To be totally honest, I almost hate the fact that I enjoy this so much. The thing about it is that I just adore this authors work, I'm just drawn to it.
I also feel like this work might be a bit misunderstood by the general audience, at least from what I've seen people say about it. I also don't at all feel the way I've seen people talk about Ranzou. The way I interpreted this story was simply that he was locked away, not because he was ill or different, but because the father wanted to keep him to himself. He's feral.
And even though the brother isn't a likable or pleasant character, he's a product of his environment of abuse, and can't really be blamed for it. And he was told from a young age that Ranzou was a soul sucking demon-thing, that would fuck anyone up.
And as for the mail man- he should know better, and probably does, but couldn't resist temptation. And Ranzou is a sexual creature to begin with. That's all he was and all he experienced for so long.
I usually don't go on like this in my comments, but this story just sets me off.
Tourou No Ori