On November 25, 2015, the Japan Patent Office (JPO) updated a webpage of handling procedures for examination relating to Product-by-Process (PBP) claims (http://www.jpo.go.jp/tetuzuki_e/t_tokkyo_e/product_process_C151125_e.htm ).
In the updated webpage, you can find the announcement that the interim Examination Guidelines (Interim Handling Procedures) have duly been incorporated into the Examination Handbook which now functions as a part of the JPO Examination Guidelines. You can also find new examples as to how to explain or argue that the PBP claim involves "impossible or impractical circumstances." The new examples will be helpful in studying how to respond to the clarity rejection if you would like to obtain patent protection by the PBP claims in Japan. Further, the JPO commented that they would add examples in which "impossible or impractical circumstances" exist as well as examples of non-PBP claims in April 2016.