Secret of the Haunted Mansion is a short story written and illustrated by Junji Ito. It is the fourth chapter of Voices in the Dark. The story centers on two friends as they enter in the eponymous haunted while dealing with its proprietor.
A haunted house attraction opens up in town. Although it's initially accused of being a con-trick, everyone who visits is terrified. Even the police are called to investigate. Two young boys, Kouichi and Satoshi, try to sneak into the house at night but are caught by the proprietor. He admires their nerve and allows them to explore the house free of charge.
The exhibits inside the house include ghosts, a severed head and a crucified man; all claiming to be members of the proprietor's family. The man, the proprietor's brother, explains that his brother eventually acquired magical powers and trapped his family inside the house; forcing them to obey his will. his brother son is also imprisoned in the house. The child's mother is an abomination too horrific to be described, and so the proprietor travels from town to town with the haunted house in an effort to escape from her.
The proprietor, with his mouth full of nails, is revealed to be Souichi Tsujii, appears and commands his brother, Kouichi Tsujii, not to tell the boys any more. They decide to escape, but come across a young child eating. Souichi's son is a cannibalistic monster with a mouth full of razor-sharp teeth, who is chewing on the remains of the policeman sent to investigate previously. He chases after the boys, and kills and eats Satoshi. Kouichi is pursued by Souichi, who spits a mouthful of nails at him. Kouichi is immobilized by the nails but at this point, Souichi's wife (Miss Fuchi, from Souichi's Diary of Curses), a giant and female version of their son) appears. She drags Souichi away, vowing to kill him if he ever tries to leave her again.
The following day, the haunted house is found completely deserted. Kouichi isn't sure if the events that took place inside the house are real - but Satoshi, and the policeman, are never seen again (the house is revealed as a manifestation of a nightmare of Souichi's in The Souichi Front).