Hi Nadi, oh you poor thing. It's amazing the amount of heat generated by other bodies in bed! I hope your body is just going through a hot patch and it starts to ease up soon.
My suggestion for Japan (and I'm sorry to say it will still be quite warm there) is to carry a small folding fan. If you haven't already got one you can buy one at most convenience stores or 100 yen shops for a couple of dollars. They do a great job of cooking and I've always got one in my bag.
I also put a small wet face washer in the hotel fridge/freezer and carry it in a little clip lock bag. Helps to cool down if you put it on the back of your neck. It's great for the plane too.
And turn the hotel air con up to arctic and let your hubby rug up while you enjoy the cool!
Good luck
