Ah yes, I see.
Perhaps the term "culprit" I used was not the best choice of words.
I'm guessing "mastermind" is better.
After all,
Now, I'm just throwing something out there (I really don't know if this is the case or not, but it's a scenario I've never seen anyone talk about):
What if Kinzo is the mastermind?
Even though he is dead, we cannot remove him from suspicion.
Perhaps Kinzo told his servants to commit the murders.
Maybe not even his servants; what if he told Eva or Rosa that they could become the next family head if certain people died?
Or maybe it's something we don't know about?
We know that our Battler (not the REAL one, as described in Episode 4) had some strange circumstances regarding his birth.
Although it is not stated in the Red, it is said that the second Battler was used... as part of of a conspiracy to steal the inheritance.
We also know that Battler did was not Asumu's son, but he is still Kinzo's grandson.
We also know that Battler has a sin.
For these reasons, I think that Battler is a key part of why everything happens.
So, maybe either Battler or Kinzo is responsible for the deaths.
Now, I realize that there is no evidence to support these theories.
However, as described in the novel itself, it is harmful to think the same way the entire time.
Since we do not have access to the world of Rokkenjima like Battler does, all we can do is theorize.
By making tons and tons of theories, though, we can come closer to our final answer.
So instead of thinking in terms of "what happens to change the outcome," it might be a good idea to think of "what already happened to cause the situation in the first place."
That might get us somewhere, I think.