Unable to sleep at night, Ganta Nakami is cranky in class and unpopular with his classmates. He discovers that the school observatory, once used by the now-defunct astronomy club, may be the perfect place for a nap—but he's not alone. Fellow insomniac Isaki Magari is willing to share the observatory with Nakami, and a friendship between the two begins as they bond over the most unlikely things.

The school forces the insomiacs’ re-formed astronomy club to operate as a proper club. The problem is, neither Nakami—its new president—nor the club’s adviser know a thing about astronomy. Yui Shiromaru, once a prize-winning astrophotographer, now the manager of a small-town video arcade, might just be the person they need.