In the shadowy corners of Victorian England, Ciel Phantomhive, known as "the Queen's Guard Dog," tackles the disturbing cases that endanger the realm on behalf of the monarchy. Guided by Sebastian Michaelis, a butler whose capabilities surpass human limits, Ciel employs every method necessary to complete his duties. However, deeper mysteries may lurk behind Sebastian's enigmatic presence.
Tragic events from Ciel's past cast a dark shadow over him, prompting a pact with Sebastian, a demon, to exact revenge on those who wronged him in exchange for his soul. In the present, Sebastian excels not merely as a butler but as a flawless executor of Ciel's desires, while impatiently awaiting the day he can feast on Ciel's soul. As they unravel the riddles surrounding Ciel's misfortunes, an unbreakable bond forms between them, defying both heaven and hell.