I suggest adding a .pot file.

[stein2nd]

In the translation tool “Poedit”, when loading the plugin folder, the warning message appeared: “Localization is not supported."

The following is a transcription from the displayed warning, with personal information masked:

WordPress error: “Create Content Model” プラグインはローカリゼーションに対応していません。
Name: ‘Create Content Model’

Analyzing WP directory /path/to/directory/create-content-model
not theme - lacks style.css

in /path/to/directory/create-content-model/create-content-model.php: header “Plugin Name” = “Create Content Model”

/path/to/directory/create-content-model/create-content-model.php is the main plugin file

no load_plugin_textdomain call and lacking metadata

some work is probably required to make the PHP code localization-ready
see https://developer.wordpress.org/plugins/internationalization/how-to-internationalize-your-plugin/