Rachel River

 Marena Rachelle River (born August 23, 2021), known as Rachel River' to the outside world, is the main character of the Death Note: Black Mercy spin-off Deadly Ambition''. She is the daughter of Mihaela River and Shiroi, the adoptive daughter of F and the granddaughter of Near and Hal Lidner. Through her parents, she is of mixed Norwegian, American and British ancestry, however identifies as American and resides in Los Angeles. She is only half human, as her biological father was a so-called nykr (a mythological Norwegian creature).

Pre-birth and early life
In the final chapter of Black Mercy, troll king Vinterskog is about to kill Shiroi, as a punishment for sympathizing with the humans he was supposed to infiltrate with. After several failed attempts to stop Vinterskog from killing Shiroi, Mihaela reveals that she and Shiroi were lovers and that she is, in fact, pregnant of him. While everyone is shocked by this revelation, Vinterskog responds coolly and continues into writing Shiroi's name in his Death Note. When later, he is killed, Shiroi states he is bound by ancient law to now curse all of the group, consisting of the leftover main characters, forever. He is then killed by V.

Black Mercy ends with a timeskip to four years after the birth of Mihaela and Shiroi's child. Mihaela is now married to F, lives in Japan and gets visits from M, her boyfriend, V and Mihaela's stepfather. It is also revealed Mihaela and F have raised Shiroi's child together, and named her Maren. The final scene of Black Mercy consists of Mihaela looking at the bed she gave birth to Maren; a coal black spot is still visible. This is a hint to Maren's half-nykr ancestry.

Personality
Rachel is shown as very resistant against her direct family, refusing to accept F as her father after learning her biological father was someone else. She has hard feelings against her mother, finding herself unable to cope with the fact Mihaela has always made very clear, quote, "it wasn't easy for [her] to have [Rachel]". She legally changed her birth certificate so that her name would be River instead of her birthname, Maren Rachelle Ferrera, and holds a grudge against her half-siblings, 10-year old Estelle and 5-year old Nicholas. Additionally, she moved to Los Angeles, USA, to follow a course at the local college in order to move as far away from her Japan-based parents as possible.