One day, a beautiful maid Lilith suddenly appears to Yuuri, who lost her parents in a car accident and decided to live alone as the owner of the remaining mansion. Lilith is a hard-working and serious maid who offers to work in her home without a salary, but she is disproportionately beautiful and suspicious for a small mansion. Yuuri, who has no choice but to be worried about Lilith who repeats her meaningful remarks and actions, tries to reveal her purpose.