Visiting a medical clinic in Japan can be a daunting task, especially if you are new to Japan and do not possess any Japanese skills, in fact residents with even a little to medium level of Japanese skills would refrain to go to a medical clinic which does not support the English language.
I took the courage to visit a clinic in Japan which did not mention any English support and was located at a rather less trendy area of Tokyo, one where foreigners are rare.
On entering, the receptionist will greet you and ask the following in Japanese “dou shimashita?” This means what happened and how can we help you. Just point to the place where it is painful, for example in my case it was my ear, so I just found the Japanese word for ear called 耳 (mimi) and told them that the problem was with my ear. Next, they will ask for your health insurance card (hoken) and would keep it for copying purposes and finalizing the bill, so you will get this back once you are ready to make the payment after the treatment has ended.
Next they will hand over a big Japanese form called (アンケート anketo) which asks about the problem, any allergies, any big surgeries and any other medication/treatment that you may be undergoing . This form is usually in Japanese, and very rarely do they have an English version (even in most English speaking clinics), so you can discuss with them that you cannot fill most of it and they will sit with you to explain everything in simple Japanese or use a translation app to convert to English or your preferred language. Also, most doctors do know the English scientific terms of the illness and medicines, and even though they may be shy/not good in having a conversation in English, if the need arises, please feel free to speak a full sentence in English to the doctor or his assistant (most places they will understand you better if you tell your problem in English, but since they are not proficient in the language they will never talk to you directly in English.) Most Japanese can read English and understand it very well, so if you want, you can write down your problems on a sheet of paper before going and keep it as a backup for the time when they miss out on your specific details (for example if pain is too much or too less, how many days back it started and so on).
Once treatment is done they ask for generic or original drugs, generic drugs are usually lower cost than the original ones, and are not branded. I never had an issue with the generic one, but if you are willing to pay the extra 20% for the branded one please go ahead and mention them that you do not want generic drugs as by default they will go for the generic drugs. Once, the prescription is ready, they will give instruction on the dosage amount for each medicine and how to intake the medicine, this can get complicated as it is hard to remember the number of dosage and time of consuming the medicine. So, please ask them specifically to write it down (in simple English or Japanese if you can read it). You can skip asking the receptionist about this because when you go to buy the medicines from a store which is usually nearby, they will again explain the dosage in detail, and most of the times they have more free time to explain it in detail than the clinic’s receptionists.