Kage Minato is obtained through events. He was in the previous(?) lucky *, and a few weeks back, around the end of September, he was in a star wheel, and he was dropping like crazy, even I got him.

Though, I tend to have good luck when it comes to this game, I've gotten Sasori(100), Tendo, and Tobirama through boxes, so...saying "even I got him"

wouldn't be unreasonable, good luck, if you're going for him.