Monster Hunter 4. The monster figure includes all download sales of the 3DS game, which was released in the country on September 14. To top it off, the series' total sales are now more than a whopping 26 million.
You only have to wander around Tokyo with a 3DS to realize how doolally Japan is for Capcom's action-RPG. 53 of the 158 people that I StreetPass-ed during our Tokyo Game Show trip were playing Monster Hunter 4 (yup, I just counted it), and that was the week after it came out. A fair proportion of the rest were clinging on to MH3 Ultimate.