A year ago, a UFO carrying 150 aliens crash-landed off the coast of Kasai. Since no one could repair their vessel, the Japanese Government granted them the title "DearS" and made them Japanese citizens, instructing them in the language, customs, and culture of Japan. However, to help them become more accustomed to human society, a homestay program was implemented to allow them to interact with other humans. On a misty morning, a truck transporting a capsule containing one of these aliens accidentally drops it onto the riverbank, freeing her from confinement. She is eventually discovered by a high school student named Takeya Ikuhara, who saves her from being struck by a truck and takes pity on her, despite his extreme distrust of their race and his desire to have nothing to do with them. After being named Ren, she imprints on him as her "Master" and serves as his personal "Slave," leaving him with a "DearS" determined to stay with him no matter what and bringing an end to his ordinary, alien-free days.