Can you tell me if there are some places in which you can enter also with tattoos?
I did some research and I found this one!
I think this is really helpful for people who have tattoos! :)
In general, Tattos are not acceptable any major Onsen. Sorry for that.
One solution is that you can rent private Onsen bath room, if hotels have that.
We call this as family bath (家族温泉).