Viki's Learn Mode is a tool that can be really useful to complement language study, but it is still in its early stages and it needs some improvements and adjustments. For example, not all korean, chinese and taiwanese shows have this option available (only those episodes with at least a 50% transcription in the original language); the dictionary also needs some adjustments and corrections here and there (so it is better to always double check the dictionary definition with the whole translated line).
There's nothing certain, but it seems there may be the possibility they add Learn Mode to japanese shows in the future:
While the feature is currently only available for Korean, Chinese and Taiwanese titles, Japanese content is likely to be available soon and other languages are being considered.
Here you can find a short tutorial:
Viki’s Learn Mode Will Take Your Language Learning To A New Level
And here you can find some opinions and more info:
- Korean drama streaming site Viki's Korean Learn Mode is now live and this is what I think so far
- Viki video streaming seeks to teach aspiring multi-linguists