Sighs....... All these tragic japanese mangas have characters with weak mindsets.
The older brother is really weak minded.
My opinion is that he should understand that what he did is right and should be proud of himself.
So what if Shiika had no one else to take care of her after her father died? The older brother might have even saved her of being raped by her own father in the future, it seems he had a historic of rapes since Shiika seems to be born of a rape act too.
I think that up to now everything is going through the path that it should have gone (killing Shiika's father and adopring her to take care of her), it's just that all their mindsets are bad and idiotic, weak. Why think it's wrong? It's not wrong. Rapists must die, and for that to happen, someone has to kill, why bother thinking it's wrong? Having blood in your hands? Oh boy be a man, be a human being, kill to protect who needs protection <3
About Yuri, sadly she is dead and can't turn back. Spiritual talk with me? Guys, let's be real, nobody knows what comes after death, so it's better to think death is the end of life and nothing comes after it, we are just a mass of meat who can think, and we will die someday and that's the end, nothing more than it.
If these characters were real, I'd just tell them I wish them to be a happy family and stop thinking shit and pay more attention because what happened once can always happen again, this dude should know it well, there are lots of real bad people in the world, the great majority. If need to kill again, kill again, but do a better work, don't get caught for ending a piece of shit's life, sadly our rules are made to protect the wrongful people.