If the Japanese have a lot of debt, denominated in Yen, and hold a lot of other currencies (e.g. the USD) then a suddenly strong currency is not to their advantage.
Strong Yen is very advantageous to Japan at current with such a collossal rebuilding effort ahead of them and little in the way of domestic sourcing for materials. If they’re not still too dazed, smart forward thinkers would capitalize and secure contracts now. The pendulum will swing back the other way soon enough.