Is there an AI learning function in YarakuZen (personalized translation)?

Yes, there is.

YarakuZen's personalized translation is a machine translation that is personalized for each user based on the machine learning results using registered phrases.

When you register your translation to Phrases, YarakuZen is using it for machine-learning, so it will be automatically edited next time similar expression appears.

Machine learning is based on words and phrases, and it takes into account the before and after context.

Therefore, depending on the context, it may not work, and it may not be the same expression every time. 

Please visit the AI Translation page for more information.