Houtarou Oreki is a high school student who tries to conserve as much energy as possible, getting involved only in matters he deems absolutely necessary. Consequently, when his older sister forces him to join the Classics Club to prevent it from disbanding, he finds the situation terribly inconvenient. To his surprise, Oreki discovers that the Classics Club already has one member: the inquisitive Eru Chitanda. Shortly thereafter, Oreki's friends—the knowledgeable Satoshi Fukube and the headstrong Mayaka Ibara—also join. Although the club has no set activities, Chitanda's constant curiosity soon drags the members into various mystery-solving escapades. The Koten-bu Series revolves around the members of the Classics Club as their eccentric daily activities gradually begin to brighten Oreki's drab way of life.