Netflix’s live-action remake of the popular Death Note manga and anime came with a lot of changes, many of which have been criticized by fans. However, the movie still sticks to many of the same concepts, with the same characters returning and, of course, the Death Note itself. That being said, the movie does introduce one new Death Note rule that could have massive implications.
Midway through the Death Note movie, Mia manages to get her hands on a page of the notebook. She writes down Light’s name and sets his death for midnight, then requests that Light hand over the notebook to her. If Light complies, Mia promises to destroy the page, which will prevent his death. Later, as Light confronts her on top of a Ferris wheel, the wheel collapses and Mia falls to her death. The ending then reveals that this was all part of Light’s long convoluted plan, as he wrote her death in a way that would destroy the page and throw L off his scent.
Erasing a name from the notebook to prevent death has never been a rule in the Death Note manga or anime, but it certainly comes with many uses. While Mia still ultimately met her end, her use of the rule was actually quite smart. She just didn’t count on Light killing her first. But there’s no doubt that in the hands of someone smarter, the rule could be incredibly powerful and advantageous.
Writing people’s names in the notebook and offering to erase it would be a very easy way to threaten them and force them to do one's bidding. Moreover, Light from the manga probably could’ve used this rule to stage his death. After L found out about the notebook's existence, Light could’ve written his own name in the notebook and had L find it. Then Light could’ve destroyed the page and faked his death, with L being left none the wiser that Light is still out there killing criminals. At the same time, Light may have seen faking his death as somewhat of a defeat, which he’s definitely against.
Despite the interesting implications of this rule, there’s been no indication that it will be made canon in the more popular Death Note manga. The Netflix adaptation had the challenge of condensing 37 episodes of an anime into a single feature-length film. And so, many changes, like this new take-back rule, were implemented to speed things along, resulting in an adaptation that has been criticized by many.