Insomniacs After School High schooler Ganta Nakami has trouble falling asleep most nights. As a result, he is irritable at school, always searching for an opportunity to find a secluded place to doze off. On the other hand, Isaki Magari is a free spirit who is well liked by her friends, but no one is aware of her sleep disorder. She makes use of the school's abandoned astronomy club observatory as her secret sleeping bunker when she needs to get some shut-eye. As fate would have it, Nakami finds Magari napping in the observatory. When Magari discovers that she and Nakami have something in common, she offers to share her secret sleeping spot with her fellow insomniac. As the two find warmth in each other's company, the struggles they face start to become easier to confront.