The Bizarre Hikizuri Siblings; Narumi's Boyfriend, also titled Sleuth Kids: The Second Daughter's Lover, is the fourth chapter from volume 13 of the Horror World of Junji Ito Collection, The Circus is Here.
Kotani receives a phone call from his former classmate Narumi Hikizuri, who tells him she plans to commit suicide by jumping off a bridge near his home. He goes to the bridge to meet her and talk her out of it. Narumi says that life at home with her siblings has become intolerable; they have been alone since their parents died several years ago. Kotani allows Narumi to stay with him for a while.
The Hikizuris' eldest son Kazuya is now the head of the family and takes care of the others: Kinako, Shigorou, Narumi, Hitoshi and Misako. Kazuya is upset at Narumi's disappearance, accusing her of being selfish and trying to make him worry. He wants the whole family to look for her. Meanwhile, Kotani is becoming fed up with Narumi, who is lazy, untidy and wastes his money. He tries to ask her to leave but she threatens suicide again, forcing him to allow her to stay. Shigorou spots Narumi on Kotani's balcony, and drags her back to the Hikizuri house.
Narumi is angry to have been brought back to her family. Kazuya decides that Kotani must be punished for seducing Narumi, and the family argues over what to do with him. Narumi announces that she can't take any more and is going to kill herself; she goes out to the garden and sets herself on fire in front of her siblings. Kotani hears the news and is somewhat upset even though he knows he should be relieved she's gone.
Shigorou tells Kotani that Narumi left a suicide note about how Kotani broke her heart. He insists Kotani come to the Hikizuri house to pay respects. The Hikizuris have placed Narumi's charred corpse on a futon, and insist he atone for her death by spending the night on the futon with her. They force him onto the futon, accidentally knocking off Narumi's head. Kotani is horrified but the Hikizuris wrap him in the futon and roll him around, insisting he should suffer for what he's done. Kotani finally manages to get out of the futon, and runs through the house trying to escape. As he runs down a hallway, he sees Narumi standing at the end; causing him to have a heart attack and drop dead from the shock.
The Hikizuris discuss what to do with Kotani's body, and blame Narumi. It is revealed that she wasn't really dead at all and her "body" was just a mannequin that she set on fire instead. They decide to bury Kotani with the mannequin, and that from now on the Hikizuri siblings will live in peace together. Narumi says she can't believe they thought she was ever serious about killing herself.