Maybe you have a look at youtube first?
There are so many, that I don't know, what to choose for you.
The Sado school alone is a longer story, some friends of friends have been there some time ago, but to be honest, there are many local groups all over Japan. If you are from Belgium, you may find some there too. In Germany we now have several ones growing, in case you feel like attending.
The best would be to ask for a kind of Belgium/Japanese society in your case (to my knowledge, you have one, but I don't know their exact name). They usually can tell you, where to go. Or you contact your Japanese Embassy directly, they are also very happy to pass on in general!