Beyond Birthday

Beyond Birthday (also known as Backup/B, BB) was the 2nd child taken in at Wammy's House, in an attempt to create a successor for L, and was the serial killer behind the Los Angeles BB Murder Case.

He did not appear in the manga, anime, or film series, but the BB Case was briefly alluded to in both manga and anime. He was born with Shinigami Eyes, which allowed him to see and know when exactly people around him would die, as well as knowing their full names. It is unknown how he could have possibly been born with the eyes, though Mello wonders if a Shinigami dropped its eyeball to Earth (instead of a Death Note).

History
Little is known about B, though him and A (real name unknown) were the first two children in line to succeed L. The pressure of Wammy's proved to be too great, though, and A committed suicide, while B wound up running away at some point.

His whereabouts remained unknown from May 2002 to the beginning of the story, L having tracked cases around the world to search for him. Beyond Birthday came up with a plan to surpass L, as the "World's Greatest Criminal", giving him a case that he would make sure he couldn't solve.

Believe Bridesmaid
Beyond Birthday's first known victim was the freelance writer known as Believe Bridesmaid, whom he killed July 31st, 2002, after drugging and then asphyxiating him with a rope. Four Wara Ningyo (straw dolls) were left at the crime scene, and in post-mortem mutilation, Bridesmaid's chest had been slashed several times, the killer having taken the time to redress him as well. When looking at the autopsy photos, Naomi Misora found that the wounds were made to resemble letters (in actuality, a Roman Numeral code spelling out the name of the next victim).

Quarter Queen
The second murder happened four days later, on August 4th. The victim, Quarter Queen (a 13 year old girl), was also drugged before her death, the cause of which was blunt force trauma to her skull. Her eyes were also crushed in further post-mortem mutilation. Three Wara Ningyo were left at the scene of the crime.

Backyard Bottomslash
The third killing happened nine days after Quarter Queen's murder. Backyard Bottomslash was a 28 year old bank worker, who had also been drugged before her death, though her age fell inbetween the previous two victims' (44 and 13) Her death was caused from loss of blood, with her right leg and left arm hacked off. Two Wara Ningyo were found nailed to the walls in a similar manner to the other two cases.

Fate
On August 22nd, Naomi arrives at the place that the next BB murder will be committed at, and comes to realize that Ryuzaki Rue, the mysterious young man she has been working with, isn't what he seems. After having figured 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.

Two years later, on January 21st 2004, Beyond Birthday dies of a heart attack in prison, presumably one of the many criminals killed by Kira (Light Yagami).

Disguise
Throughout the novel, the reader is initially unaware that Ryuzaki Rue, believed to be L in person, is in fact Beyond Birthday in disguise, using makeup to mimic L's features and his acting skills to pass off as a copy of the L he knew. The undisguised Beyond Birthday is mentioned at points in the novel, though no description is given to how he actually looks. It is mentioned that he practices his laughter.