In a fateful childhood encounter, Mira Kinohata met a stargazing dreamer named Ao Manaka. Though their time together was short, Ao showed Mira the wonders of astronomy, from orbiting planets to distant stars. Before they parted, Mira learned that a star with her name exists, but there are none with Ao's. And so, she forged a promise: one day, she would discover a new asteroid and name it after Ao.

Years later, Mira is still fascinated with astronomy. Now in high school at Hoshizaki Academy, she tries to join the Astronomy Club. Unfortunately, she finds out that the club has been merged with the Geology Club to form a single Earth Sciences Club. She joins this new club and finds a pleasant surprise—she reunites with Ao after years of separation.

Alongside their new clubmates, Mira and Ao begin their journey together to fulfill their promise. How hard could it possibly be to find an asteroid?