There is a prevalent but small group of anti-foreigner activists in Japan (I forgot their name), and I'm betting they're the ones who are staging these protests. I saw one of their protests once, and a lot of the locals around me were embarassed because I and a few other whities had witnessed it.

Anyway, I wouldn't say Japan is completely accepting of foreigners, but their attitudes are changing gradually. While I lived there, I met a lot of locals who were internationally minded and didn't treat me like an outsider. And Korean language/culture is popular with a lot of young people.