If USD 5Y bond is 3% and JPY 5Y bond is 0%, and you think you can profit by multinational exposure you can exchange your JPY for USD and buy and hold the US 5Y bond. You will gain 3% per year and you will have considerable FX risk and you will also expect those gains to diminish because the USDJPY FX rate will be forecast to fall...
If you want to hedge your FX exposure you will instead of doing a spot FX transaction do a cross-currency swap (XCS). As part of that derivative you essentially swap the higher USD IBOR rates back to lower JPY IBOR rates, and the FX transaction at the end of the 3Y is effectively pre-determined (hence why you now have no FX risk). Since forward FX rates are calculated through XCS instruments USDJPY FX will be forecast to decline over time.
In summary, the actual expected gain in JPY terms of your USD asset is related to the yield of the USD asset above US-LIBOR and the JPY/USD XCS basis.
When you look at FX markets you have the spot FX price and the XCS basis (which determine the forward FX prices). The dollar can weaken against the yen in spot terms but if the term structure of the JPY/USD XCS basis curve becomes more negative then these multi-national hedged exposures become more expensive.