At the clinic you can get a prescription for doxycycline. The charge is not covered by Japanese Health Insurance, but its cost is reasonable. If you stay two weeks in the country, you will have to start
the drug two days before your departure, and then you can stop anytime after you come back home if you feel you are fine (four weeks is the longest limit, if you are a very careful person). The charge is about 3,000 JYN for the prescription of
doxycycline for 6 weeks.