I needed a Japanese language pack and paid for most of the translation on this website:https://gengo.com
My friend checked it and he said it looked alright there are probably a few mistakes probably but it is at-least not as bad as an google translation.
The full front page is translated not the backend (admin) there are probably still some words missing but it is pretty complete.
Please help update it further on my github:
You can see the language pack in work on my website at:
Feel free to give a donation on the website above or below with the Paypal button if you like it so we can share the translation cost.
I use the following add-ons on my site they are included with the translation front end only also:
Auto Language Switcher
External Accounts Extended