Private onsen in Kansai w/o ryokan

I'm a foreign exchange student from the United States to Kwansei Gakuin University in Nishonomiya.

My girlfriend has made plans to come visit the Kansai area for a little over the week, and has expressed an interest in onsen. I'm a huge fan of the onsen, and I go often with other male friends or male members of my host family. However, my girlfriend has expressed interest in going to an onsen where we could bathe together. (after all, it seems rather pointless for her to come half-way across to the world to see me, only to sit alone in a bath)

So I began researching private onsen. All the leads I've come up with so far were private onsen offered at ryokan.
My girlfriend and I already have hotel reservations, so we have no desire to stay at a ryokan. However, does anyone have any experience using private onsen? Is it possible to use a private onsen without staying the night? Are there any specific private onsen venues (as in, private onsens which are not also ryokan)?
We're looking for private onsen in the Kansai area.

Any help would be greatly appreciated. Thank you in advance!

Is it possible to use a private onsen without staying the night?

Yes, it is possible at some ryokan. Not possible at others.

Are there any specific private onsen venues (as in, private onsens which are not also ryokan)?

Yes, a few public baths also have private baths.

We're looking for private onsen in the Kansai area.

Here you go:
http://www.kashikiri-onsen.com/kinki/kinki.html

I recommend Kinosaki Onsen:
http://www.japan-guide.com/e/e3525.html