Energy-conservative high school student Houtarou Oreki ends up with more than he bargained for when he signs up for the Classics Club at his sister's behest—especially when he realizes how deep-rooted the club's history really is. Begrudgingly, Oreki is dragged into an investigation concerning the 45-year-old mystery that surrounds the club room. Accompanied by his fellow club members, the knowledgeable Satoshi Fukube, the stern but benign Mayaka Ibara, and the ever-curious Eru Chitanda, Oreki must combat deadlines and lack of information with resourcefulness and hidden talent, in order to not only find the truth buried beneath the dust of works created years before them, but of other small side cases as well.

High school student Aya Tsukimori becomes cursed and is unable to leave her school dormitory. Meanwhile, many students begin reporting ghost sightings at the school, while others go missing and are later discovered to have drowned mysteriously. Soon, Aya attempts to communicate with fellow student Michi Kazato, who begins investigating the disappearances of her friends.

Two socially awkward young women live a seemingly laid-back life in a shared house with others - when they're not working as elite assassins.