Penty,
My main issues with tattoos in languages you don't speak - particularly non-Roman-alphabet ones (harder to infer meaning) - is the risk of poor translation. Even if you get someone to translate it for you, you can never be sure they've not deliberately done it wrong... (this is assuming you don't speak/read Japanese - if you're confident enough to check a translation, that's a whole other story)
As for the Judo-club-logo-thing, ultimately it's your body and your decision, but it might be kinda armadilloty to get it if the guy is strictly anti-tattoo.