Miki Dezaki, who first arrived in Japan on a teacher exchange program in 2007, wanted to learn about the nation that his parents had once called home.

He taught English, explored the country and affectionately chronicled his cross-cultural adventures on social media, most recently on YouTube, where he gained a small following for videos like "Hitchhiking Okinawa" and the truly cringe-worthy "What Americans think of Japan." One of them, on the experience of being gay in Japan, attracted 75,000 views and dozens of thoughtful comments.

Dezaki didn't think the reaction to his latest video was going to be any different, but he was wrong. "If I should have anticipated something, I should have anticipated the Net 'uyoku' (rightwingers)," he said, referring to the informal army of young, hyper-nationalist Japanese Web users who tend to descend on any article — or person — they perceive as critical of Japan.