Add eSIM option missing on my Japanese iPhone

• Go to Settings > Cellular, do you see Set Up Cellular or Add eSIM? Can you carrier add the eSIM?
• Go to Settings > Screen Time > Content and Privacy Restrictions > Make sure Cellular is set to Allow for changes.
• Go to Settings > General > About. What is the 5 digit model number? If you don't see it tap it once more.

Some versions of the XS Max do not support eSIM.

Tap Settings > General > About > Model Number

When you tap on Model Number, another 5 character number will appear. For example......A2104

If you see A2104, this version does not support eSIM since it was designed for use in China.

The iPhone will only display the information that is provided by the carrier that you are using.

Contact your carrier to ask them why the sSIM option does not appear.