Hiya again.- I'm studying abroad there (my purpose)
- I'm rather thin (no flabby stomach)
- I would never wear something that shows midriff.
- I'm a pretty modest dresser
hmm, it seems to me that your clothes don't have a big problem. Because you visit Japan not as a fashion model, but as a student, don't be so nervous. Japan is NOT a Muslim country where severe clothes regulation is required socially. Basically, you can wear almost everthing except controversial tiny clothes of Brazillian samba dancers.
Several months after you reach somewhere in Japan, you will notice a cultural difference between what most tourists wear in Japan and what ordinary Japanese girls wear while walking outside, as mentioned above by John B digs Japan. At first, enjoy your school life, then adjust yourself slowly to your friends.
Take look at these YouTube videos:http://www.youtube.com/watch?v=Psk6eqwoZd4http://www.youtube.com/watch?v=z3AebKC0Nwc
This is popular South Korean girls band T-ara (my favorite South Korean band). Like T-ara girls, young girls wearing short hot pants, tall high heels and fashinable tops can be seen everywhere in South Korean and Japanese cities.
If you visit Shibuya, Harajuku or Omotesando of central Tokyo, you will see young girls wearing weird and controversial fancy dress, but as long as you study at a school in rural Japan, you can spend most of your days with wearing off-brand T-shirts (sooner or later, your friends will kindly show you what to wear in your daily life).
At last, before visiting Japan, I recommend you to cut all hairs on your armpits and legs enough. As you may not know, almost all young girls here in Japan take care of their eyebrows, eyelashes, armpit hairs and other hairs almost everyday to keep their body clean. It is often said among the Japanese that women tourists in Japan forget to cut their armpit hairs. Womens' armpit hairs are taken to be something very disappointing for most Japanese people. Due to cultural differences, cutting armpit hairs enough might be more important than what to wear.