I'm sure other posters will comment on the years of deflation, the reluctance of the Japanese consummer to spend , the value of the Yen hurting exports and the % of debt versus GDP.
All I can say is that in respect of my SIPP I have dipped my toe in Japanese funds on several occassions and have taken a haircut every time. I'm staying out until I see some consistent and sustainable movement in their market.
JC