Etiquette with Onsen and Tattoos

So I know I probably can't get into an Onsen, because I have a ton of tattoos all over my arms... But my best friend, who's coming with me for our first time to Japan, has one tattoo on her thigh. Would this be troublesome for an onsen? She is not Asian, so clearly a Japanese person would not confuse her for a local.

If she can hide the tatoo on her thigh with towel(assuming the tatoo is small), no one can be seen the tatoo in Onsen.

Or cover up the tattoo plaster or band-aid.

as long as it is covered and not visible during her trip to onsen then it should be OK.

There are some places which allow tattoos - but only for Westerners (or non-Japanese).

For example, there is a cheap place in Ito (K's House) which allows tattoos - along with giving advice on other places which allow tattoos as well. I'm not spruiking them - but there are quite a few places like this which allow tattoos but they tend to be quite western friendly.

K house allows tatoos?

Talking about the public bath on the first floor and not the two private ones?

K house allows tatoos?

Not talking about the two private ones?
But if you have a private bath no one cares

I'm assuming I can't get away with it right? Because I have like a half sleeve and tattoos all over my arms and my back...

If you want to stay over in a hot spring inn, and want to use the hot spring bath, you might want to look for ones that have "kashikiri buro" (rent-to-yourself bath) or "kazoku buro" (family bath) that a family or a group can rent to themselves, for time slots of 50 minutes or 1 hour or so.

More expensive places have a hot spring bathtub/bathing area as an annex to your room, but those tend to be quite expensive.