The price change is normal for Apple, which periodically updates App Store and, at times, retail store pricing in an ongoing effort to bring uniformity across its international businesses in light of the always tumultuous foreign exchange market.
As seen in the above email, provided by AppleInsider reader Peter, the increased retail price will affect Japan only, likely a result of the country's recent economic woes and continued recovery against the dollar.
Apple did not detail how far it plans to adjust upwards, though it could be similar to a 2011 price jump that affected the UK. At the time, lower-priced apps were bumped from ?0.59 to ?0.69, while more expensive titles saw changes of over ?2.
The email also notifies developers that the new Pricing Matrix for Japan can be viewed on iTunes Connect, while updates to the Paid Applications contracts will be made available after the price adjustment goes live.
As of this writing, it is Thursday morning in Japan, meaning the new prices should be rolling out soon. A check with the iOS and Mac App Stores in that region did not yet reveal Apple's new prices.