My exchange program just finished today and it was probably the most amazing experience ive ever had, so I absolutely wish that your experience is the same is mine! The Japanese doctors and medical students work incredibly hard and there is so much to learn!
To answer your question, my suggestion would be simply to buy a japanese textbook. I bought a textbook called 病気が見える, specifically the neurology one. The Kanji it uses is all sorts of messed up but the thing I learned from my four weeks here is that if you have a detailed understanding of a particular medical topic in English, the translation isnt all that difficult once you look up the word because you inherently understand, this is especially true when it comes to anatomy. The harder part comes when you have to present in Japanese, which is slightly different way to the japanese (at least at the hospital I studied at) do it. In english we just say “45 yo M presents with acute onset…” but its really hard to translate how they do it. If you translate it word for word, the doctors just look at you funny. Luckily there are english-japanese textbooks that have example sentences of each language in a typical presentation, so that may be worth checking out.
Mostly, you will learn the most when you actually do it 
My listening has gotten at least a little bit better than 4 weeks ago, even though it was tiring sometimes 
Standing in a 9 hour radical histerectomy while concentrating on the japanese the whole time really pushes you. But i’d do it again.