The Ōmuta murders (大牟田殺人? Ōmuta Satsujin) were committed by the leader family of Kitamura-gumi (北村組?). The Yakuza gang was based in Omuta, Fukuoka, Japan, and was affiliated with the Dojin-kai crime syndicate. The four family members were sentenced to death for the murder of four people between 18 September and 20 September 2004.
On September 18, 2004, Mami, her husband and two sons strangled Sayoko and shot dead Sayoko's 18-year-old son Tatsuyuki Takami (高見 龍幸? Takami Tatsuyuki) and his 17-year-old friend Junichi Hara (原 純一? Hara Jun'ichi). They put the victims in a car, which they sent into a river. On September 20, they strangled Sayoko's 15-year-old son Joji Takami (高見 穣吏? Takami Jōji).
The half-naked body of Joji was found on September 21. When the police arrested Mami on September 22, she confessed to the killing of the other three victims. The police found the car containing the bodies of the three victims in the Suwa River in Omuta.
Mami's husband Jitsuo Kitamura (北村 実雄? Kitamura Jitsuo) was the leader of Kitamura-gumi. Her first son, Takashi Kitamura (北村 孝? Kitamura Takashi) was the son of Mami's former husband and had become Jitsuo's stepson. Her second son was Takahiro Kitamura (北村 孝紘? Kitamura Takahiro). Both Takashi and Takahiro were former sumo wrestlers, known respectively as Kyokuryūjin (旭竜神?) and Miikezan (三池山?), with the family name Ishibashi.
Jitsuo made an unsuccessful attempt to kill himself with a handgun. Takashi escaped from the police, but was recaptured. Jitsuo insisted that he had committed the murders alone, but the police regarded Mami as the main offender.
They were disruptive during their trials. On October 17, 2006, Mami and Takahiro were sentenced to death. Jitsuo and Takashi were sentenced to death on February 28, 2007. On December 25, 2007, the Fukuoka high court upheld the original sentence for Mami and Takahiro, and then Takahiro screamed in the court, "Merry Christmas". On March 27, 2008, the Fukuoka high court also upheld the original sentence for Jitsuo and Takashi.
- 三池山 孝紘 (in Japanese). Retrieved 2008-03-18.
- 福岡高裁「身勝手極まりない」…母と二男、２審も死刑判決 (in Japanese). Yomiuri Shimbun. 2007-12-26. Archived from the original on 2008-02-01. Retrieved 2008-03-18.
- "Upheld death sentences ensures family that slays together, stays together". HDR Japan. 2008-03-27. Retrieved 2008-06-21.
- Mob wife arrested for dumping body The Japan Times September 23, 2004
- Mom, boys pulled from watery grave following yakuza wife's The Japan Times September 25, 2004
- Arrest made over bodies found in river The Japan Times September 26, 2004
- Murder suspect escapes unlocked interrogation room The Japan Times November 14, 2004
- Mobster's wife, son to hang for four murders in 2004 The Japan Times October 18, 2006
- Mom, son's death sentences upheld The Japan Times December 26, 2007