I just wanted to let prospective students know that a report of mine on the English-taught LL.M. got published last December (in German, sorry):

http://www.ordnungderwissenschaft.de/2016-1/pdf/01_2016_05_raetz_das_LL.M.-studium_in_japan_odw.pdf

For those who don't read German, I might still write something in English, but you can also contact me directly and I'll try my best to respond.