Hibari Horai was adopted by his foster father at the age of six and sent to the Shinomiya household, where he became the personal attendant to a certain young lady, Kaguya. Unlike Miss Ai Hayasaka, who took care of the young lady's daily needs, the boy's main concern was her safety.
If everything went according to his foster father's plan, the boy would finish his work as Kaguya's attendant on the day he graduated high school, alongside the blonde maid. Then he would go to Italy to find his sworn elder brother and never return.
Aside from that, the boy was never supposed to have much to do with the young lady at all.
But after starting high school, he noticed that the Kaguya he was supposed to protect seemed to have grown increasingly strange since entering puberty. The same went for the blonde maid, Hayasaka.
Then one day, as he happened to pass by the girl's bedroom, he heard a familiar voice tinged with pain...
