Death Note
So after watching this anime for like the fifth time, I realized that it has a HUGE contradiction. In episode 12, Rem explains to Misa how a Shinigami dies, saying that a Shinigami should only kill people to shorten their life, not to prolong it. So does this mean that EVERY single person that is killed using the death note would not have killed someone else in their natural lifespan? I find that pretty hard to believe. Great anime nevertheless.
There's no way they can kill someone if they died already. The death of that person ends the possibility of them killing anyone. Think of it as a change in reality