Miku Onodera, a college student looking for a job, wanders into a mysterious café called “Emerald.” It was a café run by her eccentric older brother, Mahiro, and her younger brother, Yuki, who was so handsome he could be mistaken for a prince. Mikuni, who was accidentally saved by Yuki, finds herself drawn to him, but he's a high school student, has a sharp tongue, is a sadist, and to top it all off, he's a “detective”…!?