Keita Amano's average elementary school life is turned on its head when he finds a capsule machine on the way to school. Upon opening a capsule-shaped rock from the machine, Keita frees the youkai Whisper, who expresses his gratitude and declares himself Keita's personal butler from then on. Whisper also bestows upon Keita the Youkai Watch, a device that allows its user to see and make contracts with the youkai around them.

Soon, Keita sees a wide variety of youkai causing mayhem in his everyday life. With the help of Whisper and his growing list of supernatural friends, Keita begins to mend the relationship between humanity and the youkai without even realizing it.