[5] The precursor to the Matsuba-kai was the Sekine-gumi (関根組), a yakuza gang founded in Sumida, Tokyo in 1936 by a bakuto named Masaru Sekine.

The Sekine-gumi rapidly expanded, but in 1947 many members were arrested by US occupation authorities for firearms possession, resulting in the group's disbandment.

[4] In April 1960, Matsuba-kai thugs ransacked the Tokyo headquarters of the Mainichi Shimbun newspaper in revenge for unfavorable coverage.

[6] In late 1960 and early 1961, members of the Matsuba-kai mounted protests outside the offices of the literary magazine Chūō Kōron in protest of magazine's publication of Shichirō Fukazawa's short story "The Tale of an Elegant Dream” (Fūryū mutan), which described the beheading of the Imperial family with a guillotine.

[10] In early 2005, it was revealed that the Urayasu-based cleaning company contracted to Tokyo Disney Resort was run by a member of the Matsuba-kai, Saburō Shiga.