If you are unfamiliar with the concept the show is based on, it can't hurt to watch the first episode of "Death Note." The premiere diverges from the first manga chapter in how it sets everything up and how many people Light kills upfront, but it performs the same function in that it sets up the basics. You learn about the main character and discover his motivations, which appear noble to begin with.
We meet Light Yagami just before he finds the Death Note on the grounds of his school. He reads the instructions and, understandably, thinks it's just a joke, but he tests it out anyway and is shocked to discover that the notebook does indeed allow the user to anonymously kill a person — so long as they know their name and what they look like. Driven by a (somewhat childish) sense of justice, Light decides to become an almighty judge of good and evil in a new world he will create by killing off all criminals.
A Shinigami (gods of death in Japanese culture) named Ryuk shows himself to Light and reveals more about the notebook and the Shinigami realm, but none of that is pertinent to viewers just yet. The main conflict between Light and L doesn't really kick off until the second episode, so if you've seen "Death Note" before, "Rebirth" is totally skippable. The rules of the Death Note are established in this episode, but reiterated almost ad nauseam in the episodes that follow. The intro is not entirely filler, but it's pretty easy to pick the show up in Episode 2, the brilliant "Confrontation."
