The issue would be if you have Japanese cards. If you have the official english translation of it i.e. scan, official transcript then it would be allowed. Otherwise no.
You can also use foreign-language cards if you have the English-language card as a reference. Japanese cards also need to be sleeved in opaque card sleeves due to their different backs.
You can only use a mix of Japanese and English card's in your Deck if you have Colored sleeves wich you can't see the back side from the card... Try Black sleeve's it's the best to don't get any problems with Judges...
Or you could have the same copy as the jap card you are using in your deck. So you can also use a jap claydol if you have an english one in too as a reference.