Iwai Kankichirou

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His deceased body was discovered at the Shiraishi home.
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Kankichiro once made a living by placing advertisements in magazines to sell phony magic items and good luck charms. He held a nostalgic yearning for the postwar era when things and people were simple, and has nothing but negative things to say about the rapidly developing, ostentatious world of late. Radical in his belief that it would be better to tear down society and start over again, Kankichiro was discontent with his life spent poking around in society's cesspools to make a few coins.
When the Nejima Murders were widely reported in the media, it had a great impact on Kankichiro, as he witnessed how a single act by a single man could cause a major rift in society. Perceiving Fumichika Nejima as a great hero, he began collecting every piece of information he could find on the man.
Kankichiro was later arrested for his illegal business practices, and a chance meeting with Fumichika during his incarceration solidified his idolization. He was captivated by Fumichika's talk of black magic, and, following his release, acquired the grimoire Fumichika had hidden away.
As for Toshiko Shiraishi, Kanchiro set his sights on her after encountering her at her part-time job. When he learned that the Shiraishi family was in financial trouble and could not afford to send Michiyo to college, he turned on the charm and took advantage of their weakness by offering them money. He revealed his true colors, however, after moving in with the family, and used violence and money to keep Toshiko and Michiyo under his thumb. All the while, his belief in black magic depend, and he found a sponsor in the Hihaku corporation. Kankichiro forced the Shiraishi family to perform various rituals, with any attempts to resist being met with merciless beatings. The mother and daughter were helpless to resist.
After Hihaku offered Kankichiro great sums to intensify his work with black magic, he set his mind to sacrificing a child in order to perform a youth restoration spell. For this purpose, he chose Shuichi Shigima — the son of Harue Shigima, against whom Fumichilka held a grudge. He attempted to enlist Michiyo so as not to alarm the boy, and when she resisted, beat her mother twenty times. With Michiyo's assistance, Kankichiro kidnapped Shuichi and locked him up in the Shiraishi house, and told the young and courageous boy that he'd kill Michiyo if he tried to run.
While his actions were motivated by a personal grudge against the police, it was first and foremost an attempt to create a societal uproar and breakdown in public order — so Kankichiro painted the crime as a regular kidnapping, demanding a ransom from the family. However, because of an embargo on the press, the kidnapping did not cause a public outcry akin to that of the Nejima Murders. Infuriated, Kankichiro had Toshiko perform the sacrifice ritual by threatening to kill Michiyo if she refused. Tokisho killed Shuichi in his sleep, but the spell failed, for which Kankichiro blamed her.
Warning Michiyo to keep silent about the murder to avoid incriminating her mother, Kankichiro dumped the boy's body in a nearby river. The tiny corpse was found a week later in the Sumida River after floating through several canals in Honjo. Having drifted for days in the polluted waters, little evidence remained.
Although Kankichiro performed no further sacrifices, his devotion to black magic only increased. Toshiko and Michiyo spent their days consumed by guilt, forced to continue serving Kankichiro until the day they died.

Michiyo eventually took revenge on Kankichiro after possessing Yakko's body from beyond the grave and using Yakko's curse stone to kill him.