All seasons: sturdy, comfortable shoes or boots with good grip.
Winter (we may encounter snow): warm jacket, wollen hat, gloves, rain parker (or umbrellas provided).
Summer: sun hat, sun glasses, sun block, rain parker (or umbrellas provided), water bottle.
Spring and Autumn – either winter or summer gear as above depending on weather of the day.
What NOT to bring: your big luggage. Japan has an amazing courier system. Arrange via the Yamato courier station closest to your Tokyo/Yokohama hotel to have your big luggage couriered directly to your accommodation in Shizuoka Prefecture. Provided you meet Yamato’s drop-off deadline it should be delivered next day. Be sure to bring a change of clothes for your night in Shizuoka Prefecture before your luggage arrives from Tokyo the following day. Or you can ask your Tokyo/Yokohama hotel to arrange the courier, but unfortunately this will likely add an extra day until delivery. Courier fees are not included in tour fee.