Considering taking medication to treat your painful periods? To relieve your headache or cramps, you can get some pain reliever such as ibuprofen or aspirin in your nearby Japanese drugstores.
Most drug stores have large signs with the kanji for medicine, 薬 (kusuri) and you can buy some medications without any prescriptions.
Here are some kanji to know if you want to buy period pain killers,
整理 (せいり,seiri, means menstruation)
整理痛（せいりつう, seiritsuu, means menstruation pain, period pain)
痛み（いたみ, itami, means pain)
下腹部痛(かふくぶつう, kahukubutsuu, means lower abdominal pain)
頭痛 (ずつう, zutsuu, means headache)
Below are the samples of Japanese period pain killers that you can find in your nearby drugstores or you can buy it in amazon.co.jp
If you suffer various pains and menstrual cramps, you can buy EVE at a very affordable price
If you desire a pain reliever that is gentle on the stomach and also work fast on your headache, you can consider EVE Quick
If you find some difficulties to find the pain killers at the drugstore, you can ask the staffs and they will immediately help you to find one.
anou sumimasen, seiri tsuu kusuri wa arimasuka.
(Excuse me, do you have pain killer for menstruations?)
Hope this helps!
Enjoy your stay in Japan!