This will be very bad for rankings in Japan. I expect google will think it is a site for Japanese speaking Belgians located in Belgium. and I bet there are not many of those!

My own experience is having a .au ccTLD (Australia) means I get very little traffic from New Zealand even though they are very close by, speak the same language and culturally very similar. My content is very relevant to NZ shoppers, I just don't get any NZ traffic from google/bing. I'm attempting to get out of the trouble you are heading for here: How to target another country when my website has a ccTLD

I would go for a gTLD and target Japan in the webmaster tools.

This will be very bad for rankings in Japan. I expect google will think it is a site for Japanese speaking Belgians located in Belgium. and I bet there are not many of those!

My own experience is having a .au ccTLD (Australia) means I get very little traffic from New Zealand even though they are very close by, speak the same language and culturally very similar. My content is very relevant to NZ shoppers, I just don't get any NZ traffic from google/bing. I'm attempting to get out of the trouble you are heading for here: How to target another country when my website has a ccTLD

I would go for a gTLD and target Japan in the webmaster tools.