Karakuridouji Ultimo: Yamato is given an option to not get Ultimo and become his master. If he does this, Ultimo would go back in time and find someone else. It could be assumed that Yamato was only reincarnated because he was Ultimo's master. So wouldn't that mean if he declined teaming up with Ultimo, he woldn't be reincarnated? Present day Yamato may never have existed, with everyone else's lives going on without him. Yikes.
Wouldn't that also mean that others in the past wouldn't get reincarnated too? Such as Rune, Sayama... wow.
And their friends so far aren't reincarnations. They would have replacement friends and not even know it. Same with Yamato's mother. (and Rune and Sayama's parents for that matter.) She would have a replacement for her son and not be any the wiser.
The entire concept of Dunstan using a human soul is pretty scary. He would have had to get it from someone, right? It's not like he could just make it. He may have ripped out someone's soul, or maybe even more, for an experiment.
So if the good doji aren't allowed to kill, even if its one of their enemies, then how is Ultimo going to defeat Vice? Unless he finally forgets all of his morals, there isn't really another way to beat Vice and prove once and for all that good is more powerful than evil.
Well actually, there is. Turn the Evil Douji good. If Good is truely mightier than evil, then that is probably the only real way to win. If they took the above option, that would still be a victory for evil (if not the evil Douji), because the Good Douji would have stopped being good.
The final objective for both sides is apparently to deal with Dunston; the good Doji masters want to prevent him from causing the Hundred Machine Funeral, and the evil Doji masters want him out of the way.
Dunstan's insistence on the Hundred Machine Funeral being the final outcome. With all the powers at their disposal there has to be a million other ways for either camp to triumph without ripping each other and the whole earth to pieces.
Just because the good doji aren't "allowed" to kill doesn't mean that they physically can't. Ultimo did slice Vice in half in the second chapter, though that didn't kill him.Ultimo also killed Lady Gekko, who was innocent, might I add, just because she was a former noble. So it's more a moral thing than an actual rule.