After getting a hold of the titular notebook, Light Yagami takes it upon himself to begin killing the criminals of the world, which he views as a just action. It doesn’t take long for him to develop a bit of a God complex as some of the world view him as a savior while others believe that he’s a murderer. Since Light is, you know, killing people, the police begin to investigate the case, enlisting the help of the mysterious detective, L. In order to stay ahead of the police, Light joins them in their case to catch, well, himself.
Death Note is a pretty contained story that has spawned variations where new Death Note users get a hold of the book. With the anime only being 37 episodes, there isn’t a whole lot of filler to watch as each episode focuses on Light’s actions and how far he’ll go to purge the world of evil – or whatever it is he tells himself to sleep at night. Technically speaking, in my opinion, there’s really only one filler episode, with a handful of episodes having a bit of extra content or a few differences from the manga.
The first episode, kinda?
There’s a couple of details that differ from the manga, for example, in the anime Light has an entire “killing a bunch of criminals in a row” montage that doesn’t happen in the manga. There are a few details changed around, like when Light tests out the notebook for the first time, but the episode still contains a lot of the canon.
Episode 25 took a major turn, but part of it was filler
The episode that changed everything as the battle between Light and L came to an end with the death of L. This episode stays fairly close to the manga save for adding details like L washing Light’s feet (ah, sweet sweet symbolism), but it also changes the way L dies… kinda. In the manga, we get to see L’s last thoughts, but in the anime he dies quietly. Again, I don’t really consider this “filler.”
Definitely episode 26 (until the end)
This is the episode I consider to be filler as it’s a recap of events that have happened up to L’s death. However, don’t think you can skip the episode completely, as we get the introduction of L’s successors (Mello and Near) and a time jump five years into the future.
The final, climatic episode, sorta
The last episode still has the same outcome as the manga (Light is revealed to be Kira and dies) and even has the same result of Ryuk writing his name in the notebook, but the way it’s done is different. In the anime, Light manages to get away from the police and runs for his life, only for Ryuk to write his name in the notebook. Ryuk still writes his name in the manga, but he does it directly in front of Light. This surprises Light as he thought Ryuk would help him get away from the police. There’s also an extra chapter in the manga that shows what happened after the death of Kira. There’s a bit of a montage in the anime (mostly just showing Misa), whereas the manga jumps ahead an entire year. Overall, I’d say that Death Note has one filler episode with a couple moments that stray away from the manga.