In Japan, buying medicines is not difficult, but you can not buy any medicine you want anywhere.
There are two ways to buy prescription drugs:

– At the Hospital Pharmacy (院内処方)
Receive your medicines at the hospital counter or the pharmacy right next to the counter.

– At the pharmacy outside the hospitals (院外処方)
For small hospitals or clinics that may not sell drugs, you need to go to a designated drug store or near where you live that says 処方せん to buy prescription drugs.

When buying medicines, you have to show the pharmacists: Insurance card, Medical record handbook (薬手帳) with your name on it (if you do not have one, you need to answer some questions about your medical history or drug allergies).
In addition, the pharmacists may ask if you are taking ジェネリック医薬品(いやくひん) or not. This is a group of drugs that have been approved by the Ministry of Health, this kind of drug is cheap, and safe to use.

When receiving medicines, the pharmacists will explain carefully about the side effects if any or even warnings when using as well as how to use them. In case you do not understand thoroughly, please ask them immediately.

In addition to prescription drugs sold only in hospitals or other designated places, if you have common illnesses (e.g., colds, fever, cough, headache, etc.) you can go to the drugstore (e.g., 薬局, ドラッグストアー, くすり, ドラッグスギ, ワンツー, etc.) to buy medicines without prescription.

Vocabulary of names of common diseases:
発熱 (はつねつ): Fever, 頭痛 (ずつう): headache, 咳嗽 (がいそう): Cough, 鼻汁 (びじゅう): Runny nose, 咽頭痛 (いんとうつう): Sore throat, 発疹 (はっしん): Rash, 扁桃炎 (へんとうえん): Tonsillitis, 口内炎 (こうないえん): Canker sores, リンパ節炎 (りんぱせつえん): Swollen lymph nodes, 胸痛 (きょうつう): Chest tightness, 動悸 (どうき): Heart palpitations, 息切れ (いきぎれ): Shortness of breath, 不整脈 (ふせいみゃく): Arrhythmia, 腹痛 (ふくつう): Stomachache, 嘔気 (おうき): Nausea, 嘔吐 (おうと): Vomiting, 下痢 (げり): Diarrhea, 血便 (けつべん): Rectal Bleeding, 便秘 (べんぴ): Constipation, 腰痛 (ようつう): Back pain, 関節痛 (かんせつつう): Joint pain, 肩こり (かたこり): Shoulder pain, 神経痛 (しんけいつう): Neuralgia, めまい: Dizziness, ふらつき: Stagger, 歩行障害 (ほこうしょうがい): Gait abnormality, 不眠 (ふみん): Insomnia, 不安 (ふあん): Anxiety.

Human body parts vocabulary:
(body figure)
If you are not confident in your Japanese, you should go with someone who is good at Japanese and has knowledge of medicine.