The three Demon Kings ruling over Hell are Death Mask, Giant Lock, and Dark Night. They hold immense power and control over the sinners in their realm and punish any humans who dare to enter.
However, their authority is put to the test when their loyal followers stumble upon a young human child during a routine search. Death Mask, in particular, experiences a sudden shift in demeanor and is unable to carry out his usual merciless orders as he is taken by the innocent nature of the three-year-old. The child is named Maris and the Demon Kings take on the duty of raising and protecting him, leading to a comical spectacle of demons caring for a human on a daily basis.