While Japan's medical system is very good in many ways, it lacks some of the qualities and features that you might be used to in your home country. Most people in Japan go to the hospital outpatients centre when we would simply visit our local clinic and (hopefully!) see a familiar general practitioner. The wait to see one of the doctors at the hospitals and then pay for the visit can be quite lengthy. For you own peace of mind, we would recommend that you see a physician (general practitioner, specialist, dentist) in your own country before departure and clarify and treat any medical conditions you may have.
You may also wish to get prescriptions for and stock up on certain medications you may need. However, please be aware that there are restrictions on the quantity and type of medications you can bring into Japan with you. You should clarify this with the relevant Japanese authorities before your departure.