The price increases clearly seem to be due to exchange rate changes. The increases are keeping prices inline with U.S. prices.
The new pre-tax prices in Japan are as follows compared to current pre-tax U.S. prices:
iPhone 17 Pro Max is around ¥195,727 or $1,202 USD. Same phone in U.S. is $1,199.
iPhone 17 Pro is around ¥177,090 or $1,090 USD. Same phone in U.S. is $1,099.
iPhone 17 Air is around ¥161,636 or $995 USD. Same phone in U.S. is $999.
iPhone 17 is around ¥129,818 or $799 USD. Same phone in U.S. is $829.
iPhone 17e is around ¥98,000 or $603 USD. Same phone in U.S. is $599.
iPhone 16 is around ¥113,455 or $699 USD. Same phone in U.S. is $729.
It's not uncommon for Apple to adjust prices (up or down) due to notable exchange rate changes.