A UFO carrying 150 aliens crashed landed off the coast of Kasai a year ago. Because no one could repair their ship, the Japanese government decided to give them the title "DearS" and make them Japanese citizens, teaching them the Japanese language, customs, and culture. A home-stay program, however, has been implemented to allow them to socialize with other people in order for them to get more accustomed with human civilization. One foggy morning, a truck transporting a capsule containing one of these aliens crashes onto the riverside, liberating her from her imprisonment. She is finally spotted by Takeya Ikuhara, a high school student who saves her from being hit by a truck and takes pity on her.