When you have a stomachache during your trip in Tokyo, you are supposed to find a drugstore.
Yes it can help you to solve your problems.
Then you can find not only a medicine there,
also there are many kinds of stuff like cosmetics, candy, hair accessories, Vitamins, oral care, skin care, baby care, cleaning items, gift, etc... same as a drugstore in United States.
And most of them are localized goods made in Japan.
So it's sure you can easily find out new, rare, cheap, funny, cute, kawaii items which you have never seen in your life.
Japanese drugstores are also highly recommended to buy souvenirs for your family, friends.
This app shows drugstores (included name, address and google map) in Tokyo sorted by apea and is totally free of charge.