Japan cultivars is pretty hard to find in EU. For two reasons,
first, import citrus trees is banned from outside EU,
second, citruses in Japan are known as CTV transporters often. And nurseries, which are capable to clean budwood are not interested in such cultivars.
This is reason why enthusiasts start some japan citrus from seeds.
So, if you find some fruiting japan citrus cultivar like sudachi, or yuko in EU, they are most likely illegally imported and affected by CTV.
There is a test kit for sale for CTV in EU, but it costs cca. 80€ with shipping.
But as far as I know sudachi and yuko are not worth to grow for fruit, only as curiosity.