Beyond Birthday a personagem misteriosa

On August 22nd, Naomi arrives at the location where the next BB murder will be committed, and comes to realize that Rue Ryuuzaki, the mysterious private investigator she has been working with, isn't what he seems. After figuring out several clues, she finds that Ryuzaki is in fact Beyond Birthday, and that the final murder is actually his attempted suicide. She manages to stop B from burning himself to death, and arrests him.
A year and a half later, on January 21st 2004, Beyond Birthday dies of a heart attack in prison, presumably one of the many criminals killed by Kira. (If the events of this novel are canon to the anime as well, he would have died in 2007).

Throughout the novel, the reader is initially unaware that Rue Ryuuzaki, whom Misora thought of as just some suspicious young man, is Beyond Birthday. Readers are led to believe that he is L in person. This is because of his mannerisms and description (black hair, dark bags beneath the eyes, bad posture, love for sweets, and sitting position). It is in fact BB pretending to be L, using his acting skills to pass as a copy of the L he possibly knew or heard about. He had obviously never seen L totally in person, given the fact that he did not know L's lifespan or real name. The undisguised Beyond Birthday is mentioned at points in the novel.
Due to his resemblance to L, it is unknown if the artwork featured in DN:Another Note is Beyond Birthday or L. Some fans believe it to be L, especially since he does not have red eyes, which the fans have begun to connect with Shinigami Eyes. However, it was mentioned in the manga that it is impossible for a human to see if another human has "The Eyes" or not, making Shinigami Eyes appear normal.
Others have pointed out that it is unlikely that there would be two protagonists in the artwork, as opposed to the protagonist as well as the antagonist. In addition to that, there is a distinguishable "B" in between the two characters, implying that the character may very well in fact be Beyond Birthday. However, there is no way of knowing until it is either confirmed or denied by Tsugumi Ohba or Takeshi Obata. Beyond is actually a few inches taller than L, and his skin is a bit darker when he doesn't have makeup on. His natural eye color is unknown, though the general assumption is that he wears grey contacts to further disguise himself as L. Retrieved from "http://deathnote.wikia.com/wiki/Beyond_Birthday"