That's a good question. And I agree with you. ...you are not alone.

I would normally ask staff, but even that may be a difficult concept to get across.

The fact is Japanese are used to having everything warm inside. It is one of the reasons I don't like flying Japanese or Korean carriers TPAC....they just keep the cabin too hot....as well as all the JR trains, Shinkansen, taxis, hotel rooms, meeting rooms...etc etc...

I was once in a meeting room set to 27C...of course I was sweating...the host asked if I wanted it cooler...When I replied 'yes, please', he turned it down to 26C...LOL