Welcart assists you to build online shop system. It is developed in Japan.
We are using this for a Japan e-commerce website, it is pretty good once you get into it.
There are a number of things that really do need updating though, we have had to heavily modify the plugin core.
Generally it is doing the job and has good integration into payment gateways for Japan.
When it comes to translation, as we have a bi-lingual website, it is missing translation support in a number of areas, but we have been able to make it work.
You will need PHP and WordPress experience to make the most of this plugin.