There is a popular theory that the unnamed Shinigami featured in the anime OVA, Death Note Relight 1, is the reincarnation of Light Yagami. However, since a similar-ish Shinigami appears in the manga while Light is still in school, this is debatable.
Similarities to Light Yagami
There are supposedly several pieces of evidence for this assertion:
Appearance and Physical Design
- He wears a coat that looks very similar to the one Light was wearing when he died which also looks to be stained with what could be blood.
- He sports a red tie around his head that's similar to the tie of Light's high school uniform.
- He carries a messenger bag, almost identical to the one Light often carried with him when he was in high school.
- The Shinigami's mouth is shaped like Light's "Kira" smile.
- He also has bright red eyes, like Light's red eyes at certain points in the anime (Light's being a result of artistic coloring used during particular moments of intensity).
- Light also stands in the Shinigami Realm during the end of the second intro sequence - a possible foreshadowing of his reincarnation.
- The Unnamed Shinigami also sports goggles, which could allude to the fact that Light never made the deal for Shinigami Eyes. Perhaps the goggles are some kind of backup used by Shinigami who do not have the eyes.
- In episode 24 when Light regain his memory after snatching death note from L's hands he speaks by the same voice as The Unnamed Shinigami and says: "I've won. just as planned!" especially the part "just as planned!" is a total match.
Dialogue and Actions
- In the anime Ryuk tells Light that now he has something to look forward to after he dies. (It had been stated many times in the series the humans who use Death Notes don't go to Heaven or Hell at death, however it is never said he can't go to the afterlife at all). The "now" part of that sentence suggests that perhaps only certain humans can be reincarnated as Shinigami (perhaps only ones that have used a Death Note? In that case there may be other characters such as Misa and Mikami who also became Shinigami)
- The way he tosses the apple to Ryuk, as Light did when alive.
- The Shinigami walks into a bright flash of light at the top of the stairs.
- He walks with something of a limp, which could be related to the injuries Light sustained when shot several times by Matsuda.
- Ryuk himself has some vague dialogue that could be interpreted as him referring to the Unnamed Shinigami as Light: After looking at his own Death Note, Ryuk speaks to Light as if he were there; "You were not God. You were just...gone already?" This could mean Ryuk was addressing the unnamed Shinigami as Light or that he was simply reminiscing.
- Ryuk also allegedly addresses the shinigami as Light when he asks "Wouldn't you agree, Light!?" at the very end of the special.
- The shinigami doesn't stay to hear the end of the story, which could imply he already knows how it ends.
- In the Human world, Rem said "All shinigami's ingestive system is either rotten or "evolved" and that they don't need substances to sustain themselves." Since, Light knows that only Ryuk likes the apples. He recalled at least some memories about Ryuk as he remembers him as a friend.
An unnamed Shinigami appears in the manga which looks very similar to the unnamed Shinigami in the Relight series, however, there are several differences in the appearance as well, so it is unlikely that this is the same Shinigami. Not to mention that Ohba said that there are likely many Shinigami with skulls for heads.
Another reason why this argument could be considered invalid is the fact that this Shinigami is seen in artwork in the manga in which his skull is purple, not white like the one in the anime.
Continuity differences in Main Death Note and Relight films
Death Note Relight 1 contains updated dialogue, as well as a few new scenes, but does not outright contradict the events shown in the original anime or manga. L's Successors: Death Note Relight 2 essentially rewrites everything that happened after the time-skip in the original anime, and creates a few plot holes. The story contains many small adjustments to the plot, as well as a few major ones, such as Teru Mikami and Kiyomi Takada killing the SPK (an act originally performed by the Mafia). It is told from no particular point of view, although it opens with L reviewing the events of Relight 1.
Even some of the rules of the Death Note do not apply in the Relights. It is explained in How to Use VI of the Death Note rules that the conditions for death will not be realized unless it is physically possible for that human or it is reasonably assumed to be carried out by that human. However, in the added scene where Mikami kills the Kira dissenters, one of his victims die an unnatural death by having his head do a 360 degree turn.