The fake Death Notes refer to replicas of the Death Note created as both Light and Near's plans to defeat the other. They serve as important plot devices towards the end of the series.
Plot
In a bid to finally rid himself of Near, the SPK, and the Kira Task Force, Light instructs Mikami to create a fake notebook and use the replica in public while he is being tailed by the SPK. In the meantime, Kiyomi Takada would be the one to commit the actual killings with pages from the real notebook. However, Near eventually discovers the fact that Mikami was using a fake notebook all along, and has Gevanni create the SPK's own replica to deceive Light and Mikami. Mikami ends up using the replica Gevanni and Rester created, thinking it is the real notebook, and ends up implicating both him and Light as Kira.
In other media
Film series
In Death Note: The Last Name, L creates a replica of the notebook and tricks an oblivious Light into using it on his own father, causing Light to be implicated as Kira.
Television drama
L and Watari create replicas for both Light and Mikami to use and each are tricked into writing into the notebooks when they attempt to kill L and Near respectively.
Trivia
- Before Tsugumi Ohba, the author, finalized the plan for Light's defeat through the use of fake notebooks, he originally considered a plot point in which the notebook's pages were laminated for the final confrontation but ultimately rejected this idea.
- When Light was caught by Near, he claimed that the notebook Aizawa took to the warehouse was a fake. While Light said this as a bluff, Ohba has said he thinks it might not have been entirely a lie.