Chapter three of Ma no Kakera.
Tomio (who first appeared in Futon) wanders the streets, sweating heavily and holding his hands pressed tightly against his head. He then suffers a panic attack on seeing a street fishmonger behead a fish. Crying and bleeding profusely, he goes to see his girlfriend Sonoka and begs her to help him, but she won't listen to him and is angry that he cheated on her. (It is not clear whether Sonoka is Tomio's unnamed girlfriend from Futon.) In flashbacks, it is shown that the two went to see a clairvoyant who told them they would have problems with their love life and would break up soon. This woman seduced Tomio because, she claimed, she had fallen in love with his head and it's one of the best she has ever seen. She then told him that she wanted his head for her collection of human heads. She began to strangle Tomio with a piece of her own hair, but he fought her off, although it left a permanent mark around his neck. The woman gave him a red turtleneck sweater to hide it.
She then invited Tomio to see "something interesting" which turned out to be her collection of rotting, decaying human heads suspended from the ceiling. Tomio then began to choke and bleed from the neck and realized that his head had actually been severed from his body. In the present day he explains to Sonoka that he's holding his head in place with the last of his strength. Sonoka doesn't believe him but then blood starts to pour from Tomio's neck and she sees that it's true.
Sonoka tries to call an ambulance and the doorbell rings, with the person on the other side claiming to be the paramedics - but it is the clairvoyant. She produces the Death card from her tarot deck and attempts to sever Tomio's head by the last nerve. Sonoka tries to fight her off but the woman warns her that one wrong move could cause Tomio's brains to spill out. Tomio resists the woman and she then conjures a cockroach and inserts it into his neck wound. As he screams in agony, Sonoka can take no more. She stabs the woman in the head with scissors.
The woman dissolves into a pile of hair that takes the shape of a body on the floor. Three ghostly figures that look like children appear from her. They call Tomio "Daddy" and before Sonoka can do anything else, they descend on him and pull his head off. Sonoka screams and rushes to him but then finds that his head is actually joined to his body again and he's alive. She believes the "children" were an illusion. However, the clairvoyant was real and did cast a real spell on Tomio. He now has a permanent scar around his neck and continues to hold his head in place, afraid to let go.