SM magazines
Postwar Japanese periodicals devoted to sadomasochism and fetish themes, such as Kitan Club and Uramado, which spread kinbaku imagery in print from the 1950s on.
Wikipedia’s account of Japanese bondage says kinbaku became widely popular in 1950s Japan through magazines such as Kitan Club. That Osaka monthly, published from 1947 to 1975, turned to sadomasochistic themes in 1952, printing texts, illustrations and photos that included bondage, and Wikipedia counts its bondage pictures among the reasons the practice spread in that decade.
Vanilla Gallery says the editor and illustrator Suma Toshiyuki, also known as Minomura Kō and Kita Reiko, built Kitan Club into Japan’s first specialist SM magazine; the FCCJ’s Mark Schreiber dates his arrival on its staff to 1948, when it was still a true-story magazine. Suma launched Uramado in 1956. He later illustrated for titles such as SM Select and SM Collector. Kawahara Azumi’s 2024 study compares Kitan Club with other 1950s magazines, Uramado among them.