When she was little, Mira Kinohata met a boy named Ao at a campsite in town. While gazing at the starry sky together, Mira learns that there's a star with the same name as herself, but no star named Ao. The two then promised to one day explore asteroids together and find a star to name it after him. Several years later, Mira enrolls at the Hoshizaki high school and decides to join the astronomy club to fulfill her promise. However, she learns that the astronomy club will be merged with the geological research society to form the earth science club. Reluctantly, Mira goes to the club room and is reunited with Ao Manaka, the person she made the promise to explore asteroids with, and is shocked to learn that she is a girl.

Asteroid in Love centers on Mira Kinohata, who is dreaming of joining the astronomy club, when she enters high school. Her hobby was born because of a man, whom she had promised to discover new asteroids when she was younger. However, when Mira's high school life starts, she finds out that her school only has the earth sciences club, a club that consists of the astronomy and geology clubs. What is more, Mira finds out that a man that she wanted to see again so much is actually a girl. Alongside their fellow club members, Mira and her old friend Manaka Ao take part in various astronomical activities, hoping to one day discover an asteroid.—Scientiiaa