Hi Alex,
Unfortunately, it is currently not supported to download field names in Japanese in AdWords API. You may follow our blog for any upcoming features and updates.
Regards,
Hiroyuki
Google Ads API Team
Hi Alex,
Unfortunately, it is also currently not possible to get values in Japanese in AdWords API reports. You may reach out to the Google Ads Product team via the ? icon -> Get help link to verify if this is possible via the Google Ads UI.
Regards,
Hiroyuki
Google Ads API Team