Insomniacs After School, Vol. 2 by Makoto Ojiro

[Viz] Two sleepless teenagers find kinship as they escape to their school’s astronomy observatory. 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.