i notice at the start of the events after the maintenance its easy to get jonin minato, its like everytime someone gets him you need to draw more than the 1st guy did, its like a pattern. for example the 1st guy drew minato on 3x 10 *. then next guy do 5x 10 *, then so on and so on so if u did only 9x 10 * you wont get him but the another player draw 1x 10 * can get him haha. i may be wrong though, it might me just pure luck. but they said its really lucky to draw right after maintenance or vice versa. goodluck though.