Masayuki Mizutani is an ordinary high school boy living alone in his family home after his parents relocate overseas for work. Anticipating solitude, his plans are disrupted when his classmate, Sayaka Shimizu, arrives unexpectedly. Acting as his live-in maid through an arrangement made by his parents as a favor to a family friend, Sayaka zealously dedicates herself to caring for him. Her presence thwarts his hopes for peace, as she frequently twists innocent scenarios into uncomfortably erotic misunderstandings.

Masayuki's relatively calm and sound-minded disposition contrasts sharply with Sayaka's persistent advances and tendency to interpret events through her own delusional lens. Beyond managing Sayaka, he fields persistent unwanted attention from other girls. This includes his underclassman Yuka Takamura, his younger aunt Mai Takagi, and Anna Ozono—Mai Takagi's yandere lesbian admirer, who grows jealous of Masayuki's interactions with Mai. These interactions create a harem dynamic centered around him, though Masayuki primarily reacts to others' advances rather than actively pursuing relationships himself.