Summary:
#1: Jrcach is Japanese and lives in Japan but speaks English and other languages fluently. He says he has been to Europe. He posts on Tumblr all day long so I think maybe he is NEET now.
#2: He describes his career as "academic". His old blog had a lot of articles on Kyoto City Library and other libraries so he could be a librarian or just a library fan. He started out leaking and investigating and complaining about libraries and library staff in Kyoto before he discovered Nico Nico Douga.
#3: That blog got shut down because he started harassing Keekihime and that's why he came to Tumblr. He wanted to spread drama between Japanese and English internet. Harassing Keekihime isn't just recent, he has been doing it for years since even before he came to Tumblr.
#4: He says his name means "junior cats" an is pronounced "Yurka". It actually means JRCAch. JRCA is the name of his old blog that got shut down (Japan Reference Critics Association) and ch means like 2ch the Japanese forum where he is a known troll. In fact idol threads on 2ch say "get out jrcach" in the topic and when someone is trolling on anon they say "it must be jrcach, go away jrcach."
Links:
http://jrcach.tumblr.com/https://twitter.com/JRCAchhttps://www.youtube.com/user/jrcach