In a recent New York Times opinion piece, Pure Invention author Matt Alt explains why QAnon didn't take off in Japan. In short, as a conspiracy theory, QAnon is like a 1980s American car: shoddily constructed, with low-quality components and no overall vision.
From The New York Times:
But it flopped in Japan, a country that's no stranger to conspiracy theories. Even as Western media has portrayed otherwise, there are hardly any Q followers among the Japanese and it has failed the test for the nation's conspiracy connoisseurs. "It's too naïve for our readership," Takeharu Mikami, the editor of Mu since 2005, told the Asahi Shimbun newspaper last month.