I met expats, immigrants, students from all over the world in Europe, but I didn't ever met one from Japan. Anecdotal, I know, but maybe Japan is so special that emigrating from there feels like leaving Earth.
Nitpick: emigrating means moving away for good, and relatively few people from developed countries emigrate in that sense. Perhaps you mean living abroad for study or work, being an expat or something similar.
I think there are 2 big reasons why you won't find many Japanese expats in Europe. One is the real or perceived language barrier. The level of English education in Japan is pretty low, and even people who speak passable English tend to be not confident about it.
The other reason is outlined in the article. Going abroad for college isn't prized as it is in (say) China. You're deviating from the path that society expects you to follow. You might even get strange ideas about life/work balance. Going abroad for a "skip year" sounds even worse.
