This is not an unusual happening in Japan because there are many places to help you out
This problem can be easily solved by getting to any convenience store as they will have basic sizes (S, M, L, LL) and probably just white or black colors. If you are looking for more variety than it will be easy to find a Uniqlo clothing store which has a very good selection for men and women at affordable prices.
JudithMikami
New Zealand