JAXA has been looking at this mission for some time. I'm not sure that it is an approved mission at this point. Anyone with better knowledge?
That article made it sound like it was, but I am not so sure?
As vjkane will attest, that is a problem with a lot of JAXA missions--it is not clear when they are approved or just proposals. At least with NASA missions you know when something has approval to go into development (assuming that you know how to actually find that information). I think that the Japanese have a different approach to this kind of stuff. I don't know if it is cultural, or the way their bureaucracy works (two sides of the same coin).