Light Yagami manipulates Rem into assisting him by exploiting her deep love and devotion for Misa Amane, as well as appealing to her sense of duty to protect Misa. He convinces Rem that by helping him eliminate L and other threats, he can ensure Misa's safety and happiness. Additionally, Light plays on Rem's emotions by painting himself as the victim and portraying his actions as necessary for justice and a better world. This combination of emotional manipulation and strategic reasoning effectively convinces Rem to assist Light in his plans.
