In Japan, employers have a duty to provide their employees with a yearly health check. They are required to pay for it, and they will let you do it during work hours. The contents of the examination are specified by law, and without a physician’s explicit authorization, nothing may be omitted. For many professions, including teachers, this medical examination is mandatory.
According to articles 8, 10 and 11 of the School Health Regulations, one of the requirements of the medical exam is a chest X-Ray to check for tuberculosis. If you have a serious medical reason not to take this (or any other) part of the exam, talk with your go-between. If you refuse to get the X-ray, you would have to submit proof that you do not have tuberculosis, such as the results of a tuberculin test or a sputum examination, as well as a statement that you refused to get the X-Ray. However, you should know that often the sputum examination is not enough to determine whether or not a person has tuberculosis.
It is often possible to request a lead bib to protect the reproductive organs from the effects of the X-ray, so please inquire with your go-between.
Finally, your Contracting Organization has been told that they must take special care to maintain strict confidentiality. However, not everyone follow this to the letter, so don’t be surprised if one of your coworkers finds out that you have poor eyesight, or that you are slightly overweight. If you are worried about your privacy, you can also discuss this with your go-between in advance.