Rem

Rem

The female Shinigami who first gives Misa her Death Note and "eyes." Similar to Ryuk, Rem possesses two Death Notes; however, she purposely gives one of them to Misa Amane. Rem inherited her second Death Note from Jealous, another Shinigami who died when he saved Misa's life, and thought it only right to pass it on to Misa. Oddly enough, Rem inherits Jealous' love for Misa as well and is prompt to defend Misa even at the cost of her life. She shows this when she openly shows her lack of trust for Light, stating that she will kill him if Misa dies before her time.

(information from http://en.wikipedia.org/wiki/Death_Note)