travelling solo - onsen

hi there,
i'll travel to japan alone in aug and i;d love to book a hotelin Nikko area that has onsen. however, it seems that all of them don't hv a single room for solo travellers. i'd been in a onsen hotel in hakone last summer. i juz walked-in and luckily they only charged me for a single person for a double room. this time, i'd love to visit Nikko and experience the onsen again. hope someone can give me some suggestions and advice. thanks a lot!!

I thought all Japanese hotels charge per person, not per room, so being charged for one person in a double room would not be unusual.

Most ryokans won't reserve a room for a single traveller, because they DO charge per person, and if they can book two - four people in that room they'll make more money. As you've found though, they'd rather fill the room than leave it empty, if it comes to that.
There are some nice hot-spring resorts near Nikko though that have multiple ryokans, like Nikko Yumoto and Kinugawa. One hotel in Kinugawa, Hanasenkyo, advertises that they take single travellers on weeknights...japanese website only,http://www.hanasenkyo.jp/
Your best bet trying to find a place on the day is to go on a weekday, to one of the larger resort areas. There may be tourist information offices at Yumoto or Kinugawa, that can make reservations, though often these offices offer limited English.
You could also contact www.japaneseguesthouses.com to see if they can help.