Whilst writing about my night in an Inn in Hakone - very romantic, it's where my Fiance and I fell in love (we'd gone there as friends) I remembered something not so pleasant.

Mosquitoes .

Alas, I'd spent a couple of hours that night as a banquet for the pests, before soon-to-be-Mr LapLap remembered what the little machine was for and plugged it in (he was brought up in the UK and doesn't read Japanese). I never would have figured it out by myself.

So my advice is:
Please ask about any mosquito repelants wherever you're staying in October.
The mozzies weren't too viscious, but they were uncomfortable.