|As a detective|
|Works for||The Netherlands, Norway|
|As a Kira|
|Number of victims||8|
Shiroi (ろイ Shiroi; 28 December 2000 – 29 November 2020), real name Nykr Reidar (ニカライダ Nika Raida) is a member of F's investigation team in Death Note: Black Mercy. In secret, he is a nykr (nixie) and the spy of the Norwegian king of Trolls. Therefore he also possessed the Death Note of a Shinigami called Noir, making him the Eight Kira.
Shiroi was born in a bay near Trondheim, Norway. Some of his relatives, appearing later on in the sequel of Black Mercy, include his mother Joanna, his older brother and sister Bjorg and Vigdis, his cousin Asny and his uncle Jora. He was born as a full-blooded nixie, which signifies he grew up in the water and was not raised in human culture. Despite this, his relatives describe him as 'fairly odd' at his funeral, citing his love for humans and their society and his unconventionality as his reason to start living as a human permanently. Shiroi moved out of his family's nixie home in the bay of Trondheim at age 10, after which he earned a human passport and started living in Oslo, Norway. Some time before the series' start, he was employed by troll king Vinterskog to do his bidding. He was contacted by internationally reknown detective F when F gathered intel on the searching abilities of trolls and required a spokesperson to summon and communicate with trolls. F thus hired Shiroi to be on his team, so that he could enlist the trolls' aid in police investigations that required them, unbeknowest of Shiroi's loyalty to the troll king Vinterskog. According to his relatives, Shiroi had been blackmailed into serving Vinterskog, as Vinterskog had threatened to massacre Shiroi's family, would he refuse to be his servant. Despite this strained relationship with the trolls, Shiroi was fiercely devoted to protecting the mythological creatures from exposure or extermination, as displayed in Black Mercy's last chapter.
Shiroi was introduced in chapter 5, as F's dim-witted, pretty-looking and somewhat naive assistant. Prior to his first appereance, however, Shiroi had been given Noir's Death Note by Vinterskog, and had been instructed to kill Maaike van der Kooij, making him the "Unknown Kira" the detectives were looking for in the first chapters of the story. As F begins to look in the other Kira cases beside Maaike's, he orders Zuri to kidnap Mihaela River and forces her to bring his team into the Shinigami Realm, where he enlists the aid of shinigami Hone to manipulate Noir. Offscreen, as later revealed, Mihaela and Shiroi engage in various sexual activities, sparking their romantic interest in eachother. Later on, F utilized Shiroi's services to summon the trolls as he started suspecting Rammie of being a Kira. This time, however, F did not negotiate with the trolls, but rather threatened to kill them using a piece of Noir's Death Note, should they not obey him. The trolls locate Rammie in Paris, but Vinterskog instructs Shiroi to kill Rammie. Using a decoy, Shiroi denotes a Serbian woman, Smentijlana Zudhanovic, is to sell weapons to F's assistant Zuri, who then uses the weapons to kill Rammie and inadvertedly, herself. These events proceed as written down in Shiroi's Death Note. Additionally, Smentijlana comes forward claiming she is the Secret Kira, with M, F, and V believing her, but dies shortly thereafter as her actions were controlled by Shiroi's Death Note. After Rammie's death and therefore the destruction of Kurome's Death Note, Umi visits Vinterskog and grants him his Death Note. Now that Vinterskog has power over both Noir's Death Note, in hands of his henchman Shiroi, and Umi's Death Note, he starts massacring Norwegian politicians and prominent Norwegian celebrities. Furthermore, he uses the Death Note to send nixies after F, V and M, who are attacked by one at the swimming pool of their hotel in Norway, where they resided to investigate the new string of Death Note murders. Shiroi recognizes the creature attacking them as a nixie and kills it in order to save his comrades and Mihaela, whom he secretly has pursued a romantic relationship with. F, M and V decide to move their teams to Trondheim, suspecting Vinterskog to be behind the attack, but as the teams stay in a local hotel for the night, the hotel is flooded by nixies under Vinterskog's control, who carry out a major attack intent on killing everyone. Mihaela uses knowledge of chemistry to set off a giant explosion, but the characters are saved mainly because of Shiroi, who kills the attacking nixies using his knowledge that saying their real name will dissolve them. After surviving the attack, the teams head out to confront Vinterskog, who ultimately reveals Shiroi was his spy all along, but also announces he wishes to execute Shiroi for defying him, which Shiroi did by thwarting Vinterskog's attempts to kill the teams. Mihaela tries to stop Vinterskog, who also reveals he owns Umi's Death Note, by announcing she's carrying Shiroi's child, but Vinterskog seems determined. In reaction, the teams steal Shiroi's Death Note and with it, kill Vinterskog. Enraged, Shiroi vows that due to the death of the troll and therefore all trolls in Norway, he must "curse them forever", and transforms into full nixie form. Trying to save everyone, V shoots him and he dissolves into little black drops.