Kobayashi is about to head off to work one morning when she opens her apartment door and finds a dragon's head staring at her from the balcony. The creature promptly transforms into a cute, buxom, and lively young girl in a maid uniform, introducing herself as Tooru.
It turns out that the night before, after a drunken trip to the mountains, the stoic programmer encountered this dragon and, learning it had no place to go, offered it a home. Now Tooru has arrived to accept that offer, determined to repay Kobayashi's kindness by serving as her personal maid. Despite regretting her drunken promise and hesitating to follow through, Kobayashi is swayed by a mix of guilt and Tooru's impressive dragon abilities, ultimately allowing the girl to stay.
Though Tooru is highly efficient at her duties, her unorthodox housekeeping methods often horrify Kobayashi and sometimes create more trouble than they solve. Additionally, the circumstances surrounding the dragon's arrival on Earth prove more complicated than they first appear, as Tooru carries heavy emotions and painful memories. To make matters worse, Tooru's presence attracts other mythical beings to the home, bringing along a host of eccentric personalities. As Kobayashi does her best to navigate this chaotic situation, nothing could have prepared her for life with a dragon maid.