I first noticed WordPress had a large following in Japan after WordCamp SF 2014. It was great seeing them show up full force. Their WordCamp website for Tokyo also topped our list as the most impressive of all 2014 sites we reviewed. You could tell they put some hard work into organizing the event. I think the growth of the community can be largely attributed to great community leadership (I really like their style of MeetUps), internationalization efforts, and the culture's long standing ability to recognize great technology. I was privileged enough to visit Japan (Tokyo + Kyoto) last year... this gives me another reason to head back soon. WordCamp Tokyo here I come! :)