ero guro nansensu

Ero Guro Nansensu and Ranpo Kitan: Game of Laplace

From Ranpo Edogawa’s wikipedia page:

Although many of his first stories were primarily about sleuthing and the processes used in solving seemingly insolvable crimes, during the 1930s, he began to turn increasingly to stories that involved a combination of sensibilities often called ero guro nansensu, from the three words “eroticism, grotesquerie, and the nonsensical”. The presence of these sensibilities helped him sell his stories to the public, which was increasingly eager to read his work. One finds in these stories a frequent tendency to incorporate elements of what the Japanese at that time called “abnormal sexuality” (変態性欲 hentai seiyoku). For instance, a major portion of the plot of the novel The Demon of the Lonely Isle (孤島の鬼 Kotō no oni), serialized from January 1929 to February 1930 in the journal Morning Sun (朝日 Asahi), involves a homosexual doctor and his infatuation for another main character.

Another entry from Ranpo’s Wikipedia page:

Another of his interests, especially during the late 1940s and 1950s, was bringing attention to the work of his dear friend Jun'ichi Iwata (1900–1945), an anthropologist who had spent many years researching the history of homosexuality in Japan. During the 1930s, Edogawa and Iwata had engaged in a light-hearted competition to see who could find the most books about erotic desire between men. Edogawa dedicated himself to finding books published in the West and Iwata dedicated himself to finding books having to do with Japan. Iwata died in 1945, with only part of his work published, so Edogawa worked to have the remaining work on queer historiography published.

It all makes sense now.