As Kobayashi sets off for another day at work, she opens her apartment door only to be met by an unusually frightening sight—the head of a dragon, staring at her from across the balcony. The dragon immediately transforms into an energetic young girl dressed in a maid outfit, introducing herself as Tooru. It turns out that the stoic programmer had come across the dragon the previous night on a drunken excursion to the mountains, and since the mythical beast had nowhere else to go, she had offered the creature a place to stay in her home. Thus, Tooru had arrived to cash in on the offer, ready to repay her savior's kindness by working as her personal maidservant. To top it all off, Tooru's presence ends up attracting several other mythical beings to her new home, bringing in a host of eccentric personalities. Although Kobayashi makes her best effort to handle the crazy situation that she has found herself in, nothing has prepared her for this new life with a dragon maid.

As Tooru continues on her quest to become the greatest maid and Kanna Kamui fully immerses in her life as an elementary school student, there is not a dull day in the Kobayashi household with mischief being a daily staple. On one such day, however, a massive landslide is spotted on the hill where Kobayashi and Tooru first met—a clear display of a dragon's might. When none of the dragons they know claim responsibility, the perpetrator herself descends from the skies: Ilulu, the radical Chaos Dragon with monstrous power rivaling that of Tooru. Sickened by Tooru's involvement with humans, Ilulu resorts to the typical dragon method of resolving conflict—a battle to the death. Despite such behavior, she becomes intrigued by Kobayashi's ability to befriend dragons and decides instead to observe just what makes Kobayashi so special. With a new troublesome dragon in town, Kobayashi's eccentric life with a dragon maid is only getting merrier.