Crossover: For the Sake of World Peace

One-sentence summary: Kill 50 people to save 100. No matter the era, pure justice is always difficult for everyone to understand. For example: Thanks to some black technology whose workings are too sensitive to disclose, you travel back to ancient times and kill an innocent little boy. The consequences are disastrous. Reporters, waving microphones and video cameras, ask you emotionally, "What kind of filthy soul could have driven you to do this, to commit such a monstrous crime?!" You calmly reply, "Thirty years from now, he will launch an unjust war that wipes out humanity. I killed him, but I saved all of mankind. So I have no regrets." Then you are sentenced to immediate execution. Like I said, justice is always difficult for everyone to understand. And some justice is so uncompromising and intense that nobody but you, the one carrying it out, could ever understand it. You knew this all along. This dilemma won't frighten you away, either. You were born to be an "executor of justice." To see true justice prevail, and to preserve the world's peace as it has always been, you fear nothing. Yes, you fear nothing! I'm just writing nonsense. Don't take it seriously. Second-person perspective, a work made to mess with readers. For now, the worlds include Inuyasha, Blood Knight, and Naruto. More later. Wish fulfillment makes me happy.