As the son of a family of Onmyou mystics, 12-year-old Nakahito dreams of becoming a powerful mystic like his older brother, Kamihito. After being coerced into sneaking into Dr. Ayanokoji's secret lab by bullies, he encounters a pink-haired woman in a maid uniform. Initially, Nakahito assumes she is just a life-sized doll, but when she falls on him and their lips touch, she awakens! Now, this girl, Kurumi, is completely devoted to him, addressing him as "Master" and ready to fulfill any request he may have... provided he knows what to do with her. Nakahito is a shy and insecure child who often feels inferior to his brother's abilities. He is uncomfortable with the excessive attention Kurumi provides him. However, their relationship evolves over time.