Neylon has shoulder-length golden blonde hair and wears a pair of oval glasses. He has a heart-shaped head with a defined jawline and cheekbones. He wears a white suit.
In the video game, Neylon has tanned skin, his hair is white, and he appears to be much older.
It is indicated that Neylon is a drug addict; Rod Ross refers to this when Neylon first sees the monstrous Shinigami Sidoh and panics. Ross asks Neylon if he has been "smoking too much crack," as Sidoh is invisible to the other mafiosi until they touch the Death Note themselves.
A low-ranking member of the Mafia working under Rod Ross since 1987, Neylon was involved in drug trafficking and illegal weapons sales. Despite four separate arrests, he was cleared every time due to lack of evidence.
When the Mafia, led by Ross and Mello, manages to extract the Death Note from the Japanese Task Force, it ends up under the ownership of Neylon, even though Mello handles it several times while examining it for clues that could lead to Kira.
After Sidoh tracks down his Death Note to the Mafia's hideout, he gets Neylon to see him and persuade the others present to touch the Death Note, allowing them to see him as well. From Sidoh, they learn about the Shinigami Eyes trade which enables a human to see the names of others in exchange for half his life expectancy. Mello tells Neylon to do the trade. He initially refuses, but Ross threatens to shoot him dead on the spot if he doesn't. Ross even further tempts Neylon by telling him that making the trade would make Neylon his right-hand man.
Using her own Shinigami Eyes, Misa Amane eventually identifies Neylon as another Death Note owner since, while going through FBI files of known Mafia men, she can see his name but not his life expectancy. She passes this on to Light Yagami, who uses Misa's Death Note to have Neylon mail him the address of Mello's hideout.
Light then sends a US Army Special Forces team to raid the hide-out, but their face-covering helmets are removed by the invisible Sidoh. Their faces are picked up by security cameras and relayed to TV monitors, through which Neylon can see their names. He passes them on to Ross, who writes them in the Death Note, killing the soldiers. The Mafia then evacuated to another base.
(In the scene where he reads out the names and when he and the others are escaping in cars, Neylon has his hands behind his back and is wearing handcuffs. Although it is not specified why this is the case, it could be that Mello and Ross consider him and the Eyes as too valuable to let him wander off. He may have been caught after posting the letter to Light.)
Light has already set Neylon to die at 23:59 on November 10, 2009. Following the failure of the initial raid, he organizes a new raid with the Kira Investigation Team which is carried out at midnight on November 11, one minute after Neylon and most of the other Mafiosi have been killed by Misa's Death Note.
- In the anime, Neylon's eye trade and the first attempt to retrieve the Death Note were not included.
- According to Death Note 13: How to Read, Neylon enjoys reading a bestselling 1908 novel called Anne of Green Gables and takes a liking to brunette women. It is also stated that he dislikes Mello.
- “B-Boss… is this ugly-looking guy in the costume a new recruit or something?”
- “A shinigami? Ha! Ha!”
- “E… Everyone! Please touch this notebook! I'm not going crazy!”