2018 iPhone battery replacement in Japan
In short, just jump to the page linked below.
You’ll see everything
https://www.google.co.jp/amp/s/join.biglobe.ne.jp/mobile/sim/gurashi/iphone_battery180830/amp/
Check if you have AppleCare+ by entering your iPhone serial number!
https://checkcoverage.apple.com/us/en/
Instructions
1. check your device that you need a support this time. (By Apple support)
2. Choose “battery and charge”
3. Select “battery replacement” then choose 「持ち込み修理」
Links: