Version 1.2.1 is released.
It should be available soon in plugin section but it is better to download from Github where it is already there and up to date (plugin section one has a small error in it).
https://github.com/piloujp/ZenCartv1...ses/tag/v1.2.1
I will use this post to add a tutorial for the quickest way to install Japanese pack on a freshly installed Zen Cart v1.5.8 or v1.5.8a:

- First you need a new Zen Cart v1.5.8 or v1.5.8a already installed and working in English version but with no plugin added.
- After that backup all cart files by making a copy somewhere and Database by exporting everything in an SQL file. If something goes wrong, using these backup you can start from zero without re-installing English version.
- Then run SQL queries in 'mysql_japanese_install.sql', 'mysql_japanese_config.sql' and if you want admin fully Japanese 'mysql_japanese_admin_menu.sql'. You can do this by importing these files in a tool like phpMyAdmin or by copying queries into Zen Cart admin SQL tool or whatever you like. If some error occurs during this process, fix it before doing next step! Continuing with errors will just mess up things.
- Now copy to your cart folders 'email', 'images' and 'includes' including all files and subfolders. If you use FTP, check that everything has been uploaded.
- Finally, copy content of admin-JP (or admin-EN if you want to keep admin in English) to your cart admin folder. Don't copy folder itself has names are different for each installation.

You are done!
You still have to configure/install modules you want to use like you would do with an English version. For shipping modules have a look at readme file.

Tip: In case you run into troubles and after few fixing attempts things don't get better, start again from zero using backups. It is generally faster.