Do you have tattoos and are you interested in onsen (= hot spring)? People with a tattoo(s) are normally not permitted to enter bathing facilities in Japan. The reason is that tattoos are considered as an indication of association with yakuza crime syndicates. This tattoo-related regulations has become tricky nowadays as so many non-Japanese tourists visit Japan and tattoos are just part of their fashion statement (needless to say, some tattoos have cultural significance).
I found an interesting article on the New Zealand Herald talking about this tattoo issue. If you are interested, please have a look at the article here.