its getting hotter each day, so bring lighter clothes. If you are sensitive to the sun, be sure to bring your own sunblock lotion or you can just buy the local ones. In the afternoon and early morning, it could get a little cold, so just bring a light wrapper or long sleeves will do. It might rain , but you can always buy umbrella in convenience stores or 100yen shop.
If you need more clothes, you can always go to the nearest uniqlo and gap, they seem to be popping everywhere
Have fun on your trip