Rem (レム, Remu) is the Shinigami who gives Misa Amane one of the Death Notes she had. Like Ryuk, Rem possesses two Death Notes; however, Rem did not get hers through trickery. The Shinigami Gelus, who had fallen in love with Misa, sacrificed himself to kill her destined murderer. In doing so he was reduced to dust, leaving only his Death Note. Rem delivered this Death Note to Misa, since it was her life he saved.
While Ryuk takes amusement in everything in the Human World, Rem is almost the exact opposite, viewing most humans with contempt. Also, while Ryuk is ambivalent to Light's success or failure, Rem actively assists Misa. This makes her equally as guilty as Ryuk of not displaying 'proper' traits for a Shinigami to have. She is even willing to sacrifice her life to defend Misa, as evidenced by her threat to kill Light should Misa die before her time. For Misa's sake, however, she still assists Light in his schemes.
Death Note 13: How to Read said Rem "supposedly" experiences difficulty while writing the Japanese language.
Takeshi Obata said that Rem is his favorite Shinigami since she is "a good person," even though she is a Shinigami.
Rem was a normal Shinigami living in the Shinigami Realm and answering to the Shinigami King. She would use her Death Note to kill humans when it was their time in order to prolong her own life, while watching and observing humans in her downtime.
She became particularly interested in the goings-on of fellow Shinigami Gelus, who watched model/actress Misa Amane from the Shinigami Realm and fell in love with her. However, she was scheduled to die soon, and he did not know why. He and Rem watched her for a long time until the day she was set to die; she was attacked by a mugger. Betraying the Shinigami rules, Gelus wrote down the mugger's name in his Death Note and saved Misa's life. However, in doing so, he effectively gave his life to her, as she was not supposed to continue to live, and turned to ash and died. Rem watched the whole ordeal and retrieved Gelus' notebook, now knowing the only way to kill a Shinigami.
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