Kumatarō Kido and Yagorō Tani

Kumatarō Kido (城戸 熊太郎, Kido Kumatarō; c.1857–1893) and Yagorō Tani (谷 弥五郎, Tani Yagorō) were Japanese spree killers who killed 11 people, including an infant, on May 25, 1893, a spree known as Kawachi Jūningiri (河内十人斬り). They committed suicide after the murders, and their remains were discovered on June 7. ^[1]

Kido had entered a common-law marriage with a woman, but his wife had left him in favor of his rival Torajirō Matsunaga. Torajiro's brother Denjirō Matsunaga had assaulted Kido, and had obtained part of Kido's money by fraud. Kido decided to kill the entire Matsunaga family, and he recruited his pupil Tani as an assistant for the revenge scheme. The victims of the killing spree included Kido's ex-wife and his former mother-in-law, but the killers failed to kill Torajirō.

The roots of the killings were both emotional and financial. Kido lost his common-law-wife to a man named Torajirō Matsunaga, whose brother, Denjirō, defrauded money from Kido and assaulted him. Along with a pupil named Tani Yagorō, Kido decided to kill Matsunaga's family. They prepared hunting guns and japanese swords and on May 25, 1893, they attacked Denjirō's house and killed four people. They then attacked Denjirō's son's house, killing five people. They also killed his former common-law-wife and her mother. However, they were not able to kill Torajirō Matsunaga. They committed suicide after the murders, and their remains were discovered on June 7. A novel, Kokuhaku by Japanese punk rock singer Kō Machida, was based on their case.^[2][3]