Definitive info on Master Star series Ace I just read:
http://banpaku.bpnavi.jp/info_pass.html
Here is how you win one. You have to enter the raffle in that link for a chance to play the UFO catcher at the Banpresto event on 3/20 at Big Site in Tokyo. If you win the raffle, they will send you some kind of post card and you bring that to the event to play the UFO catcher. It is 2000 yen to play and you play until you win the item….AKA it's guaranteed. The catch is you have to win this raffle. Good luck to those trying for it.
P.S. For the 7-11 thing to clarify for people if they want to try to win the limited POP looking Luffy (assuming it is). Basically you have to buy the products below (One Piece Bento, onigiri, certain drinks, hot dogs etc). However much you spend, you divide that total by 300 yen to see how many raffle points you have (300 yen = 1 point). Then you choose which raffle you want to participate in, the t-shirt, figures, or camera. When you make your choice, they determine how many entries you have pending on # of points. AKA if you have 10 points, you can have 10 entries in the T-shirt raffle, 3 entries in the figure raffle, or 2 entries in the camera raffle. Hope this clarifies for you guys.