- This page is for the film series character who is L's successor. For the first film character who goes by this alias, see L. For the novel character who goes by the alias Rue Ryuzaki, see Beyond Birthday.
Ryuzaki has black hair with streaks of grey and dark grey eyes.
He usually wears a black coat, either black or grey clothes, and black boots. When he needs to hide his face during the Kira investigation, he wears a mask. The first mask he wears is the same mask used by L, but he later gets a similar one in grey.
Ryuzaki is a skilled detective, although he initially doubts that he can live up to L. He dismisses his friends' support by saying he's just L's backup, although he later comes to embrace his role, saying that he will be better than L.
While Near and especially J are friendly with him, Ryuzaki is a bit more reserved in his friendship. He is open with them, discussing his feelings about L and the case freely. He also shows that he cares for them when he keeps them out of the case so that they won't be at risk. He gives Near some guidance in detective work, and Near tests Ryuzaki in return, such as when he begins their conversation in Japanese to prepare him for taking the Kira case even though Ryuzaki had declined to get involved before. J and Near seem to work together to encourage Ryuzaki to take the Kira case.
Ryuzaki switches easily between speaking Cantonese and Japanese. He is presumably also fluent in English, since J speaks English to him several times. It's likely that he and J grew up speaking English together at Wammy's House.
Ryuzaki is a member of Wammy's House, but very little is known about his past. He knows J and Near from Wammy's House, and he presumably knows Mello as well since he asks Near about him. Ryuzaki refers to himself as L's backup born from IVF, suggesting that he was created from L's DNA and raised at Wammy's House specifically to be an excellent detective like L.
Ryuzaki is fully informed on the Kira investigation and the Death Notes prior to his introduction to the series, presumably from reports that L left behind for him and the other members of Wammy's House. Before his death, L made Ryuzaki promise him that he would never use a Death Note. At some point following L's death, Ryuzaki took up the title L.
Sometime in 2015 or 2016, after the Kira murders resume, the Death Note Countermeasure Task Force attempts to contact Ryuzaki to assist them on the new Kira case, but Ryuzaki declines. In 2016, in the second episode of Death Note: New Generation, Ryuzaki goes to Hong Kong for a different case, which he solves and later discusses with Near, who informs him that the Task Force has requested his assistance again.
J contacts Ryuzaki with a new case in connection with the Death Notes. An online video depicts a girl who abruptly acts strangely, as though controlled, and it's generating attention. Ryuzaki realizes that the girl's final words are an anagram for, "Kira, I have it too." J, along with Near, convince Ryuzaki to get involved, and he flies from Hong Kong to Japan to work the case with J. He locates the girl, who killed herself as controlled by a Death Note, and messages the one who killed her, although J is unable to trace the new Kira's location. The girl's computer is hacked while Ryuzaki is in the room, and the camera turns back on, but Ryuzaki wears his mask so the other Kira is unable to see his face and he shuts down the video feed.
Afterward, Ryuzaki agrees to work with the Task Force on the investigation. J offers to assist him with the Kira investigation, but Ryuzaki rejects the offer since he does not want her to risk her life with him.
- Ryuzaki shares many similarities with Beyond Birthday, although he is not an explicit adaptation of the character. Beyond Birthday exists in the film series separately, since the LABB murders happened in the film continuity, but the character has not explicitly been seen.