In 2004, 2chan went mainstream with the publication of “Train Man,” a collection of posts from the board that purportedly showed how users had helped a hapless nerd woo the woman of his dreams. The story became a best-selling book, a blockbuster movie and a popular TV show. It made 2chan the most heavily trafficked site in Japan.While most users discussed hobbies or griped about work, others threatened murder, posted bomb threats and spawned reckless conspiracy theories. A flood of posts from far-right users denied Japan’s war crimes and contributed to a nationwide rise in anti-Korean hate.As Mr. Nishimura profited handsomely from the site — earning …
