After the Weimar Rep. fell, Japan became a global hub of sexual liberalism through its free-love movement. Though it began earlier, it continued long after, spanning roughly 50 years while most other countries experienced only 10–20. Erotic art, still taboo elsewhere, helped fuel rapid growth in Japan’s entertainment industry compared with other nations until they were the kings of fiction.
While most countries had their "hippie movement" after the 50s, 60s, or 70s, Japan's started in the 1920s and arguably resurfaces again every certain amount of time.
I meant no offense; it's just that the cause of Japan's popularity is a mature topic.