Designed by Takeshi Obata, L's character was created to be Light's antagonist with his appearance contrasting Light's although during his first cameos he was intended to be a good looking man. Since his introduction in the series, L has received praise by publications from manga and anime with most of them commenting on his personality. Matsuyama's portrayal of L as well as Juliani's work as his English voice actor have also been the subject of reviewers.
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L, who also uses the aliases Hideki Ryuga, Ryuzaki, Eraldo Coil, and Deneuve, the latter two for which he has developed reputations as the second- and third-best detectives in the world, is quite secretive and only communicates with the world through his assistant Watari. He never shows his face to the world, instead representing himself with a capital L in Cloister Black font. His real name, L Lawliet, is only revealed in the guidebook Death Note 13: How to Read. When asked about L's ethnicity, Ohba responded saying "I think of him as a quarter Japanese, a quarter English, a quarter Russian and... maybe a quarter French or Italian? Something like that". After meeting the Kira investigation team, he requests that the task force refer to him as Ryuzaki for discretion. Ohba said that L is the smartest character in the manga because "the plot requires it". He added that he personally views L as "slightly evil".
L's disheveled and languid appearance masks his great powers of deduction and insight. He tends to second-guess everything he is presented with, and is extremely meticulous and analytical. He has several quirks such as preferring to crouch rather than sit, eating only sweet foods like desserts and fruits, and holding items very delicately. L stayed in England for five years, and during that time he was the champion in tennis for the England Junior Cup. In chapter 38 of the manga, L suggests that even though he eats only sweet foods, he remains underweight because the brain uses the most calories of any organ in the body. He also says that if he sits normally, his reasoning ability would drop 40%. Whenever L gives percentages to indicate how much he suspects a person of committing a crime, such as "five percent", in reality he means over 90 percent; Ohba said about L, "The truth is, he's a liar. [laughs]"
L suspects early in the investigation that Light Yagami is Kira, but cannot obtain any concrete evidence. In several situations, Light seems to be proven innocent by the circumstances, but L remains skeptical. If Light were Kira, the case would be solved, and L has trouble letting go of this simple and complete solution. L can easily present his conclusions publicly at any time, and with his reputation, is taken seriously. He also intends to tell Light that he can "take the offensive". After capturing a man who also has a Death Note, Light tricks Rem, the shinigami owner of a Death Note that she gives to Misa, into killing L for his own personal gain, making her believe that she must kill him for the sake of Misa's life. L's last sight before death is Light triumphantly smiling over him, and in his last moment L confirms to himself that Light is the first Kira.
Death Note 13: How to Read describes L in the Death Note yonkoma as the "holder of the world's greatest mind" and having the "powerful ability to act like a fool". Death Note 13: How to Read adds that in the yonkoma "it's like [L was] born to be mocked".