what to wear - shorts? trousers?

We are travelling Japan in September,covering Tokyo, Kyoto & Nara, Kansai region, western Honshu, Shikoku, and Kyushu. We are not travelling further north than Tokyo.

My questions is about clothing - it seems the country is cooling down, and there is quite a lot of rainful too. Would it be more sensible to travel mostly in shorts and trousers? Are there any social/cultural situations, or areas, where it would be unsuitable for men to wear shorts? What clothing is most suitable for this time of year?

Thanks

Hard to say as the weather may change during the day! I was in Tokyo one,in September, when the heat and humidity were terrible and wish I had been wearing shorts. Friends of mine, another year, wore casual pants, that North Americans love, with zippers running horizontally under each knee. If it is too hot you unzip the bottom part of each leg and you have shorts! OR you need to wear thin pants, have shorts in your back pack (or vice versa)and change during the day in a public washroom.Generally speaking the Japanese don't mind shorts around the knees. I saw middle age chubby Caucasian males with short shorts and low cut tank tops and it was embarrassing to look at them. A short sleeve shirt looks better and is coler than a T-shirt