[dirtyroboto]

Tattoos are a personal choice and should not be on display unless you are on personal time.
In a professional situation you should do your best to be professional, and if this means hiding your tats then so be it.
So, lets take teaching as an example...
I am teaching students and showing my tattoos, or smoking, or drinking!
The students may attach a coolness to the gaijin and wish to emulate this gaijin behavour to impress.

To show a tattoo and then befriend a student, you should know that you may cause this student to follow your heart and get a tattoo. The Japanese kids are really this impressionable.
The adverse is true in the workplace.
No exposure = no tolerence