Differences in iPhones between countries

Phones sold in different regions of the world support different LTE and 5G bands. Phones sold in Japan can not silence the camera shutter sound.

The warranty is ONLY valid in the country where the device was originally sold. You may not be able to get out of warranty service at all outside of the country of original sale.

Buy a phone in the country where you intend to use it.

Basically, at least three things come into consideration on what you are planning on doing:

1. Cellular service
2. Wi-Fi service
3. Potential phone repairs

I'll start with the last one first. Apple does not provide international support for iPhones. That means, should your iPhone require a repair, (since you intend to buy it in Japan) would have to be done in Japan. If you take the phone back with you to Germany, if it needs servicing, you would have to take it back to Japan. Apple does not provide international shipping support, so either you or someone you know, in Japan, would have to take the phone to the local Apple service center in Japan.

For phone service, all new iPhones are dual-SIM capable. I would suggest that if Germany will be your home country, that you acquire eSIM service by a German cellular provider. When, in Japan, you can get a physical SIM. Most Japan airports are equipped with SIM kiosks for that purpose.

For Wi-Fi service. This may or may not pose a problem, but different regions in the world support slightly different Wi-Fi channel ranges and transmission levels.

Ref:

• Maximum wifi transmission power per country - Wolph