They probably won't give you crap about it, 'cause you're a foreigner. Some people will probably find it interesting. Some of your students will probably think it's cool. Your school's headmaster will almost certainly NOT think it's cool.
There will be a group of people who will probably assume that you're a thug or some sort of "ne'er-do-well" because of it.
On a different note, why would anyone want to avoid onsen or beaches (unless he/she is just morbidly obese or something)? Onsen are one of my favorite things in Japan; they are glorious--especially in winter. On a really, really cold, snowy day, I like to bring a good book in a ziplock bag to the outside pool and sit and read for an hour or two. It's awesome.
I have a tattoo, but I've never had any problem in onsen. Even been into a couple of "No Tattoo" onsen.
coop52 wrote:Get a thicker skin, and let it go.
Apologies for "The Last Samurai" title. I consider that movie horrifically racist and offensive, an unfortunate perpetuation of the "white messiah" concept. If I could remove it, I would.