That's in itself a very Japanese thing - making a big declaration, that you "will retire for good, no coming back, ever", but let 3-4 years pass and you're back as if you've never made the declaration. Also happens a lot with Japanese pop bands, they do huge "farewell" shows, there is monthlong talk about how they'll split and pursue other careers, but what actually happens they just take a 1-2 year break. I've come to the conclusion that the "we retire" trick is simply a marketing ploy because it gets the attention of the Japanese domestic audience like nothing else.