In Shopify, the label of the "Add to Cart" button can normally be changed by "Editing Default Theme Content", but this is an example of a setting that allows you to specify the label for each template using the theme editor.
Example of setting to allow the product purchase button label to be changed for each template file from the theme editor
[Settings Step 1] Add a schema to "main-product.liquid" and a label to "ja.schema.json"
[Settings Step 2] Replace some of the code in main-product.liquid and buy-button.liquid
