The best thing about death note is probably the fact that it took like the three smartest people on earth, an entire police task force, the mafia, the FBI and a team literally designed to take down kira (and maybe even a couple of shinigamis dependant how you look at it) years to take down a kid with a notebook, a slightly unstable lawyer, a news reporter and a girl that’s just in it for the hell of it and yet Naomi practically figured it out before the second book had even finished
The Death Note pilot manga had a young student named Taro finding a notebook that would kill anyone whose name was written in it… and also an eraser that would resurrect those people if you erased their names.
In stark contrast to Light, Taro gets scared of the notebook and stops using it after his first two unintentional uses (although a classmate of his uses it to kill people and deflect suspicion from himself). This fits nicely with Near’s statement late in the manga that if Light were an ordinary person, he would not have used the Death Note after the first time.
Taro’s character design was later used as the inspiration for the fourth Kira, Teru Mikami.
“Vol. 13: How to Read” implies that the creator had considered having L win with Light deadand that an error between editor and artist switched Mello and Near’s character designs.
It was also said that Naomi Misora was originally going to be a more major character, but since she wound up being too clever, she had to be killed off fast. Also, Ohba had considered having Mello be the one to win against Light, but since he was also too “smart”, he had to be killed off to provide suspense.
Mogi was originally planned to have a larger role, but Ohba couldn’t decide how to do it.
An early idea was to have Near and Mello be L’s twin sons, but this was eventually dropped because L is implied to be about 25 years old when he dies, when Near and Mello are both about 14 years old. Which would imply that L became a father incredibly young.
Allegedly, early concepts for the Shinigami would have made Ryuk, Gelus, and Rem resemble attractive humans, but the decision was made that Gelus’s brief appearance worked better if he looked somewhat pathetic and Ryuk and Rem being beautiful did raise concerns that fans might side with the team of killers just because of their looks. The designs were soon changed to give the Shinigami a more appropriately inhuman feel.