Sorry I made you wait! The Singularity by Vaonis' app, which is indispensable for the operation and observation of Vespera, has been compatible with Japanese in today's update.
All menus and operations related are already compatible with Japanese. The recently added astronomical information is still in English, but it will be supported in Japanese within the next few months.
The app can be downloaded for free from the App Store or Google Play Store.
The explanation about the appHere。