Kasutori magazines カストリ雑誌
Cheap popular magazines that flooded Japan right after World War II, known for erotic and lurid content; Kitan Club, later an important SM magazine, began in this period.
Kasutori magazines were mass-market entertainment magazines that appeared in large numbers once publishing was freed after the Pacific War. Japanese Wikipedia dates the boom to roughly 1946–1949 and characterizes the titles by erotic and grotesque material, from pin-up photos to crime stories and racy fiction. Writing for the FCCJ, Mark Schreiber notes they were printed on cheap recycled paper.
The name refers to kasutori, a cheap postwar shōchū. Japanese Wikipedia gives two explanations: just as three gō of the drink left a person collapsed, most magazines folded by their third issue; or the word was read as “scraps” for the coarse paper. Kitan Club, which Schreiber says was first published in Osaka in November 1947, outlived the boom and turned into an SM magazine; Japanese Wikipedia lists it, running 1947–1975, among the titles that later switched to SM.