It is quite common these days for those who index to be 100% equities, just up until retirement, or longer.
How do you plan to de-risk, the yen makes many tradition strategies less palatable.
Japanese Government bonds -> Almost no yield
Japanese Government inflation index bonds -> See above
Developed Country foreign Government Bonds AA+ etc (Treasuries/Gilts/Etc) -> Currency Risk
Gold -> No Yield
(J-Reits, Corporate bonds, Equity funds, Privately held real estate, etc}
by Choice_Vegetable557