If you are using the matchmaking option, then port forward the default ports, both TCP and UDP : 46318. (I'm not even sure it's necessary for the matchmaking option.)
If you are using the direct connect option, you have the option to host on a port that you specify, therefore you must port forward whatever port you told it to host on, but the default is : 46318.
With out readable error messages, it's hard to say why you are getting errors in matchmaking. But I'd guess it's because you are not in Japan, and are just timing out to whoever you are connecting to, who is prolly in Japan. I'd recommend getting on IRC, finding someone to play there, and using the direct connect option to play.