Houtarou Oreki, a high school student with a penchant for conserving energy, reluctantly joins the Classics Club at his sister's behest to prevent its dissolution. Surprised to find the club's sole member, the curious Eru Chitanda, Oreki's world is further disrupted when his friends Satoshi Fukube and Mayaka Ibara also become part of the group. Despite the lack of defined club activities, Chitanda's insatiable curiosity leads the members into a series of intriguing mysteries. The Koten-bu Series follows the eccentric daily interactions of the Classics Club members, gradually adding color to Oreki's mundane existence.