Why the exchange rate matters
Suppose an ETF holds U.S. shares. Their prices can change in dollars, while the ETF’s value is shown in yen. A stronger or weaker yen can therefore change your yen return even if the share prices stay the same.
Hedged and unhedged funds
An unhedged ETF leaves currency movements in the yen return. A hedged ETF aims to reduce them. Hedging has costs and does not remove every currency effect.
For a useful comparison, look at funds that follow similar assets. Check the index, hedging policy, trust fee, and trading unit on each fund page.