It’s a great question, and I’m afraid there’s no simple answer! Japan has its own rich indigenous sexual history, following a trajectory almost completely unperturbed by the West up until the Meiji Restoration in 1868. Elements of torture and BDSM have been present in Japanese culture for centuries, long before the Marquis de Sade (1740-1814) came to define the term “sadism.” Rope bondage, for instance, can be traced back to the martial art of Hojojutsu, estimated to be over 1,000 years old.
In Gay Erotic Art in Japan Vol. 1, Gengoroh Tagame follows the origins of contemporary Japanese gay erotic art to the hentai zasshi (“perverse magazines”) of the post-war era, which allowed all kinds of erotica to co-exist: heterosexual, gay, lesbian, fetish and S&M. These magazines, like Fuzokukitan, were the platform for a generation of gay artists whose work frequently focused on BDSM, including Go Mishima, Tatsuji Okawa, and Sanshi Funayama.
Nowadays, the incidence of BDSM actually seems much lower than it was half a century ago in Japanese gay erotic art. There’s a lot more room for a variety of sexual tastes in contemporary gay manga, so it usually depends on each artist’s personal predilections. Clearly, BDSM is essential to the erotic tastes of Gengoroh Tagame, which accounts for its frequent appearance on this blog— but while BDSM isn’t entirely absent from in the work of mangaka such as Kazuhide Ichikawa and Seizoh Ebisubashi, it’s perhaps less central to their practice.
The erotic themes in gay manga also have a lot to do with which magazine is paying for it. If a mangaka is hired by SM-Z, their work is going to be bondagey. If it’s for Samson, it’s going to feature an older male character. For G-men, the characters might have a more “macho” look. So BDSM is just one “flavor” available in the Japanese gay marketplace, and hence gay manga.